Manual transmission
Overview
 
A manual transmission, also known as a manual gearbox or standard transmission (informally, a manual; standard, straight shift; stick (shift), (US); or straight drive) is a type of transmission
Transmission (mechanics)
A machine consists of a power source and a power transmission system, which provides controlled application of the power. Merriam-Webster defines transmission as: an assembly of parts including the speed-changing gears and the propeller shaft by which the power is transmitted from an engine to a...

 used in motor vehicle
Motor vehicle
A motor vehicle or road vehicle is a self-propelled wheeled vehicle that does not operate on rails, such as trains or trolleys. The vehicle propulsion is provided by an engine or motor, usually by an internal combustion engine, or an electric motor, or some combination of the two, such as hybrid...

 applications. It generally uses a driver-operated clutch
Clutch
A clutch is a mechanical device which provides for the transmission of power from one component to another...

, typically operated by a foot pedal (automobile) or hand lever (motorcycle), for regulating torque
Torque
Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....

 transfer from the internal combustion engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...

 to the transmission, and a gear stick
Gear stick
A gear stick is the lever used to change gear in a vehicle, such as an automobile, with manual transmission or several common forms of automatic transmission.The device is used to change gear; in a manual transmission vehicle this will normally be done whilst depressing...

, either operated by foot (as on a motorcycle) or by hand (as in an automobile).

A conventional manual transmission is frequently the base equipment in a car; other options include automated transmissions such as an automatic transmission
Automatic transmission
An automatic transmission is one type of motor vehicle transmission that can automatically change gear ratios as the vehicle moves, freeing the driver from having to shift gears manually...

 (often a manumatic
Manumatic
Manumatic is a portmanteau of the words manual and automatic, that applies to a class of automotive transmissions.Manumatic refers to an automatic transmission that allows convenient driver control of gear selection. This type of transmission was introduced in the 1990s...

), a semi-automatic transmission
Semi-automatic transmission
A semi-automatic transmission is an automobile transmission that does not change gears automatically, but rather facilitates manual gear changes by dispensing with the need to press...

, or a continuously variable transmission
Continuously variable transmission
A continuously variable transmission is a transmission that can change steplessly through an infinite number of effective gear ratios between maximum and minimum values. This contrasts with other mechanical transmissions that offer a fixed number of gear ratios...

 (CVT).
Manual transmissions often feature a driver
Driving
Driving is the controlled operation and movement of a land vehicle, such as a car, truck or bus.Although direct operation of a bicycle and a mounted animal are commonly referred to as riding, such operators are legally considered drivers and are required to obey the rules of the road...

-operated clutch
Clutch
A clutch is a mechanical device which provides for the transmission of power from one component to another...

 and a movable gear stick
Gear stick
A gear stick is the lever used to change gear in a vehicle, such as an automobile, with manual transmission or several common forms of automatic transmission.The device is used to change gear; in a manual transmission vehicle this will normally be done whilst depressing...

.
Encyclopedia
A manual transmission, also known as a manual gearbox or standard transmission (informally, a manual; standard, straight shift; stick (shift), (US); or straight drive) is a type of transmission
Transmission (mechanics)
A machine consists of a power source and a power transmission system, which provides controlled application of the power. Merriam-Webster defines transmission as: an assembly of parts including the speed-changing gears and the propeller shaft by which the power is transmitted from an engine to a...

 used in motor vehicle
Motor vehicle
A motor vehicle or road vehicle is a self-propelled wheeled vehicle that does not operate on rails, such as trains or trolleys. The vehicle propulsion is provided by an engine or motor, usually by an internal combustion engine, or an electric motor, or some combination of the two, such as hybrid...

 applications. It generally uses a driver-operated clutch
Clutch
A clutch is a mechanical device which provides for the transmission of power from one component to another...

, typically operated by a foot pedal (automobile) or hand lever (motorcycle), for regulating torque
Torque
Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....

 transfer from the internal combustion engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...

 to the transmission, and a gear stick
Gear stick
A gear stick is the lever used to change gear in a vehicle, such as an automobile, with manual transmission or several common forms of automatic transmission.The device is used to change gear; in a manual transmission vehicle this will normally be done whilst depressing...

, either operated by foot (as on a motorcycle) or by hand (as in an automobile).

A conventional manual transmission is frequently the base equipment in a car; other options include automated transmissions such as an automatic transmission
Automatic transmission
An automatic transmission is one type of motor vehicle transmission that can automatically change gear ratios as the vehicle moves, freeing the driver from having to shift gears manually...

 (often a manumatic
Manumatic
Manumatic is a portmanteau of the words manual and automatic, that applies to a class of automotive transmissions.Manumatic refers to an automatic transmission that allows convenient driver control of gear selection. This type of transmission was introduced in the 1990s...

), a semi-automatic transmission
Semi-automatic transmission
A semi-automatic transmission is an automobile transmission that does not change gears automatically, but rather facilitates manual gear changes by dispensing with the need to press...

, or a continuously variable transmission
Continuously variable transmission
A continuously variable transmission is a transmission that can change steplessly through an infinite number of effective gear ratios between maximum and minimum values. This contrasts with other mechanical transmissions that offer a fixed number of gear ratios...

 (CVT).

Overview

Manual transmissions often feature a driver
Driving
Driving is the controlled operation and movement of a land vehicle, such as a car, truck or bus.Although direct operation of a bicycle and a mounted animal are commonly referred to as riding, such operators are legally considered drivers and are required to obey the rules of the road...

-operated clutch
Clutch
A clutch is a mechanical device which provides for the transmission of power from one component to another...

 and a movable gear stick
Gear stick
A gear stick is the lever used to change gear in a vehicle, such as an automobile, with manual transmission or several common forms of automatic transmission.The device is used to change gear; in a manual transmission vehicle this will normally be done whilst depressing...

. Most automobile manual transmissions allow the driver to select any forward gear ratio
Gear ratio
The gear ratio of a gear train is the ratio of the angular velocity of the input gear to the angular velocity of the output gear, also known as the speed ratio of the gear train. The gear ratio can be computed directly from the numbers of teeth of the various gears that engage to form the gear...

 ("gear") at any time, but some, such as those commonly mounted on motorcycle
Motorcycle
A motorcycle is a single-track, two-wheeled motor vehicle. Motorcycles vary considerably depending on the task for which they are designed, such as long distance travel, navigating congested urban traffic, cruising, sport and racing, or off-road conditions.Motorcycles are one of the most...

s and some types of racing cars, only allow the driver to select the next-higher or next-lower gear. This type of transmission is sometimes called a sequential manual transmission
Sequential manual transmission
A sequential manual transmission is a type of manual transmission used on motorcycles and high-performance cars for auto racing, where gears are selected in order, and direct access to specific gears is not possible....

. Sequential transmissions are commonly used in auto racing for their ability to make quick shifts.

Manual transmissions are characterized by gear ratios that are selectable by locking selected gear pairs to the output shaft inside the transmission. Conversely, most automatic transmission
Automatic transmission
An automatic transmission is one type of motor vehicle transmission that can automatically change gear ratios as the vehicle moves, freeing the driver from having to shift gears manually...

s feature epicyclic
Epicyclic gearing
Epicyclic gearing or planetary gearing is a gear system consisting of one or more outer gears, or planet gears, revolving about a central, or sun gear. Typically, the planet gears are mounted on a movable arm or carrier which itself may rotate relative to the sun gear...

 (planetary
Epicyclic gearing
Epicyclic gearing or planetary gearing is a gear system consisting of one or more outer gears, or planet gears, revolving about a central, or sun gear. Typically, the planet gears are mounted on a movable arm or carrier which itself may rotate relative to the sun gear...

) gearing controlled by brake bands and/or clutch packs to select gear ratio. Automatic transmission
Automatic transmission
An automatic transmission is one type of motor vehicle transmission that can automatically change gear ratios as the vehicle moves, freeing the driver from having to shift gears manually...

s that allow the driver to manually select the current gear are called Manumatic
Manumatic
Manumatic is a portmanteau of the words manual and automatic, that applies to a class of automotive transmissions.Manumatic refers to an automatic transmission that allows convenient driver control of gear selection. This type of transmission was introduced in the 1990s...

s. A manual-style transmission operated by computer is often called an automated transmission rather than an automatic.

Contemporary automobile manual transmissions typically use four to six forward gears and one reverse gear, although automobile manual transmissions have been built with as few as two and as many as eight gears. Transmission for heavy trucks and other heavy equipment usually have at least 9 gears so the transmission can offer both a wide range of gears and close gear ratios to keep the engine running in the power band
Power band
The power band of an engine or electric motor refers to the range of operating speeds under which an the engine or motor is able to operate efficiently...

. Some heavy vehicle transmissions have dozens of gears, but many are duplicates, introduced as an accident of combining gear sets, or introduced to simplify shifting. Some manuals are referred to by the number of forward gears they offer (e.g., 5-speed) as a way of distinguishing between automatic or other available manual transmissions. Similarly, a 5-speed automatic transmission is referred to as a "5-speed automatic."

Unsynchronized transmission

The earliest form of a manual transmission is thought to have been invented by Louis-René Panhard and Emile Levassor in the late 19th century. This type of transmission offered multiple gear ratios and, in most cases, reverse. The gears were typically engaged by sliding them on their shafts (hence the phrase shifting gears), which required a lot of careful timing and throttle
Throttle
A throttle is the mechanism by which the flow of a fluid is managed by constriction or obstruction. An engine's power can be increased or decreased by the restriction of inlet gases , but usually decreased. The term throttle has come to refer, informally and incorrectly, to any mechanism by which...

 manipulation when shifting, so that the gears would be spinning at roughly the same speed when engaged; otherwise, the teeth would refuse to mesh. These transmissions are called sliding mesh transmissions or sometimes crash boxes
Crash gearbox
A crash gearbox, also known as a crash box, is a transmission type used in old cars, trucks, and other automotive vehicles. It is more properly called a "sliding mesh" gearbox and has the nickname "crash" because it is difficult to change gears, so gear changes are often accompanied by loud noises...

, because of the difficulty in changing gears and the loud grinding sound that often accompanied. Newer manual transmissions on cars have all gears mesh at all times and are referred to as constant-mesh transmissions, with "synchro-mesh" being a further refinement of the constant mesh principle.

In both types, a particular gear combination can only be engaged when the two parts to engage (either gears or clutches) are at the same speed. To shift to a higher gear, the transmission is put in neutral and the engine allowed to slow down until the transmission parts for the next gear are at a proper speed to engage. The vehicle also slows while in neutral and that slows other transmission parts, so the time in neutral depends on the grade, wind, and other such factors. To shift to a lower gear, the transmission is put in neutral and the throttle is used to speed up the engine and thus the relevant transmission parts, to match speeds for engaging the next lower gear. For both upshifts and downshifts, the clutch is released (engaged) while in neutral. Some drivers use the clutch only for starting from a stop, and shifts are done without the clutch. Other drivers will depress (disengage) the clutch, shift to neutral, then engage the clutch momentarily to force transmission parts to match the engine speed, then depress the clutch again to shift to the next gear, a process called double clutch
Double clutch
A double clutch is a driving procedure primarily used for vehicles with an unsynchronized manual transmission...

ing. Double clutching is easier to get smooth, as speeds that are close but not quite matched need to speed up or slow down only transmission parts, whereas with the clutch engaged to the engine, mismatched speeds are fighting the rotational inertia and power of the engine.

Even though automobile and light truck transmissions are now almost universally synchronised, transmissions for heavy truck
Truck
A truck or lorry is a motor vehicle designed to transport cargo. Trucks vary greatly in size, power, and configuration, with the smallest being mechanically similar to an automobile...

s and machinery, motorcycles, and for dedicated racing are usually not. Non-synchronized transmission
Non-synchronous transmission
A non-synchronous transmission is a form of transmission based on gears that do not use synchronizing mechanisms. They are found primarily in various types of agricultural, and commercial vehicles...

 designs are used for several reasons. The friction material, such as brass
Brass
Brass is an alloy of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties.In comparison, bronze is principally an alloy of copper and tin...

, in synchronizers is more prone to wear and breakage than gears, which are forged steel, and the simplicity of the mechanism improves reliability and reduces cost. In addition, the process of shifting a synchromesh transmission is slower than that of shifting a non-synchromesh transmission. For racing of production-based transmissions, sometimes half the teeth (or dogs
Dog (engineering)
In engineering a dog is a tool that prevents movement or imparts movement by offering physical obstruction or engagement of some kind. It may hold another object in place by blocking it, clamping it, or otherwise obstructing its movement...

) on the synchros are removed to speed the shifting process, at the expense of greater wear.

Heavy duty trucks often use unsynchronized transmissions, though military trucks usually have synchronized transmissions, allowing untrained personnel to operate them in emergencies. In the United States, traffic safety rules refer to non-synchronous transmission
Non-synchronous transmission
A non-synchronous transmission is a form of transmission based on gears that do not use synchronizing mechanisms. They are found primarily in various types of agricultural, and commercial vehicles...

s in classes of larger commercial motor vehicles. In Europe, heavy duty trucks use synchronized gearboxes as standard.

Similarly, most modern motorcycles use unsynchronized transmissions: their low gear inertias and higher strengths mean that forcing the gears to alter speed is not damaging, and the pedal operated selector on modern motorcycles is not conducive to having the long shift time
Shift time
Shift time refers to the time interval between gear changes in a transmission during which power delivery is interrupted. This is usually in reference to motor vehicles but can apply to any gearbox. Reducing shift time is important in performance vehicles or race cars because during shifting the...

 of a synchronized gearbox. Because of this, it is necessary to synchronize gear speeds by blipping the throttle when shifting into a lower gear on a motorcycle.

Synchronized transmission

Most modern manual-transmission vehicles are fitted with a synchronized gear box. Transmission gears are always in mesh and rotating, but gears on one shaft can freely rotate or be locked to the shaft. The locking mechanism for a gear consists of a collar (or dog collar
Dog clutch
A dog clutch is a type of clutch that couples two rotating shafts or other rotating components not by friction but by interference. The two parts of the clutch are designed such that one will push the other, causing both to rotate at the same speed and will never slip.Dog clutches are used where...

) on the shaft which is able to slide sideways so that teeth (or dogs) on its inner surface bridge two circular rings with teeth on their outer circumference: one attached to the gear, one to the shaft. When the rings are bridged by the collar, that particular gear is rotationally locked to the shaft and determines the output speed of the transmission. The gearshift lever manipulates the collars using a set of linkages
Linkage (mechanical)
A mechanical linkage is an assembly of bodies connected together to manage forces and movement. The movement of a body, or link, is studied using geometry so the link is considered to be rigid. The connections between links are modeled as providing ideal movement, pure rotation or sliding for...

, so arranged so that one collar may be permitted to lock only one gear at any one time; when "shifting gears", the locking collar from one gear is disengaged before that of another is engaged. One collar often serves for two gears; sliding in one direction selects one transmission speed, in the other direction selects another.

In a synchromesh gearbox, to correctly match the speed of the gear to that of the shaft as the gear is engaged the collar initially applies a force to a cone-shaped brass clutch attached to the gear, which brings the speeds to match prior to the collar locking into place. The collar is prevented from bridging the locking rings when the speeds are mismatched by synchro rings (also called blocker rings or baulk rings, the latter being spelled balk in the U.S.). The synchro ring rotates slightly due to the frictional torque from the cone clutch. In this position, the dog clutch is prevented from engaging. The brass clutch ring gradually causes parts to spin at the same speed. When they do spin the same speed, there is no more torque from the cone clutch and the dog clutch is allowed to fall in to engagement. In a modern gearbox, the action of all of these components is so smooth and fast it is hardly noticed.

The modern cone system was developed by Porsche
Porsche
Porsche Automobil Holding SE, usually shortened to Porsche SE a Societas Europaea or European Public Company, is a German based holding company with investments in the automotive industry....

 and introduced in the 1952 Porsche 356
Porsche 356
The Porsche 356 was the company's first production automobile. It was a lightweight and nimble handling rear-engine rear-wheel-drive 2 door sports car available in hardtop coupe and open configurations. Design innovations continued during the years of manufacture, contributing to its motorsports...

; cone synchronisers were called Porsche-type for many years after this. In the early 1950s, only the second-third shift was synchromesh in most cars, requiring only a single synchro and a simple linkage; drivers' manuals in cars suggested that if the driver needed to shift from second to first, it was best to come to a complete stop then shift into first and start up again. With continuing sophistication of mechanical development, fully synchromesh transmissions with three speeds, then four, and then five, became universal by the 1980s. Many modern manual transmission cars, especially sports cars, now offer six speeds.

Reverse gear is usually not synchromesh, as there is only one reverse gear in the normal automotive transmission and changing gears into reverse while moving is not required. Among the cars that have synchromesh in reverse are the 1995-2000 Ford Contour and Mercury Mystique, '00-'05 Chevrolet Cavalier, Mercedes 190 2.3-16, the V6 equipped Alfa Romeo GTV/Spider (916)
Alfa Romeo GTV & Spider
The Alfa Romeo GTV and Alfa Romeo Spider were two sports cars produced by the Italian manufacturer Alfa Romeo from 1995 to 2006....

, certain Chrysler, Jeep, and GM products which use the New Venture NV3500 and NV3550 units, the European Ford Sierra and Granada/Scorpio equipped with the MT75 gearbox, the Volvo 850, and almost all Lamborghini
Lamborghini
Automobili Lamborghini S.p.A., commonly referred to as Lamborghini , is an Italian car manufacturer. The company was founded by manufacturing magnate Ferruccio Lamborghini in 1963, with the objective of producing a refined grand touring car to compete with established offerings from marques like...

s and BMW
BMW
Bayerische Motoren Werke AG is a German automobile, motorcycle and engine manufacturing company founded in 1916. It also owns and produces the Mini marque, and is the parent company of Rolls-Royce Motor Cars. BMW produces motorcycles under BMW Motorrad and Husqvarna brands...

s.

Shafts

Like other transmissions, a manual transmission has several shafts with various gears and other components attached to them. Typically, a rear-wheel-drive transmission has three shafts: an input shaft, a countershaft and an output shaft. The countershaft is sometimes called a layshaft.

In a rear-wheel-drive transmission, the input and output shaft lie along the same line, and may in fact be combined into a single shaft within the transmission. This single shaft is called a mainshaft. The input and output ends of this combined shaft rotate independently, at different speeds, which is possible because one piece slides into a hollow bore in the other piece, where it is supported by a bearing. Sometimes the term mainshaft refers to just the input shaft or just the output shaft, rather than the entire assembly.

In many transmissions the input and output components of the mainshaft can be locked together to create a 1:1 gear ratio, causing the power flow to bypass the countershaft. The mainshaft then behaves like a single, solid shaft: a situation referred to as direct drive.

Even in transmissions that do not feature direct drive, it's an advantage for the input and output to lie along the same line, because this reduces the amount of torsion
Torsion (mechanics)
In solid mechanics, torsion is the twisting of an object due to an applied torque. In sections perpendicular to the torque axis, the resultant shear stress in this section is perpendicular to the radius....

 that the transmission case has to bear.

Under one possible design, the transmission's input shaft has just one pinion gear, which drives the countershaft. Along the countershaft are mounted gears of various sizes, which rotate when the input shaft rotates. These gears correspond to the forward speeds and reverse. Each of the forward gears on the countershaft is permanently meshed with a corresponding gear on the output shaft. However, these driven gears are not rigidly attached to the output shaft: although the shaft runs through them, they spin independently of it, which is made possible by bearings
Bearing (mechanical)
A bearing is a device to allow constrained relative motion between two or more parts, typically rotation or linear movement. Bearings may be classified broadly according to the motions they allow and according to their principle of operation as well as by the directions of applied loads they can...

 in their hubs. Reverse is typically implemented differently, see the section on Reverse.

Most front-wheel-drive transmissions for transverse engine mounting are designed differently. For one thing, they have an integral final drive and differential. For another, they usually have only two shafts; input and countershaft, sometimes called input and output. The input shaft runs the whole length of the gearbox, and there is no separate input pinion. At the end of the second (counter/output) shaft is a pinion gear that mates with the ring gear on the differential.

Front-wheel and rear-wheel-drive transmissions operate similarly. When the transmission is put in neutral and the clutch is disengaged, the input shaft, clutch disk and countershaft can continue to rotate under their own inertia. In this state, the engine, the input shaft and clutch, and the output shaft all rotate independently.

Dog clutch

Among many different types of clutches, a dog clutch provides non-slip coupling of two rotating members. It is not at all suited to intentional slipping, in contrast with the foot-operated friction clutch of a manual-transmission car.

The gear selector does not engage or disengage the actual gear teeth which are permanently meshed. Rather, the action of the gear selector is to lock one of the freely spinning gears to the shaft that runs through its hub. The shaft then spins together with that gear. The output shaft's speed relative to the countershaft is determined by the ratio of the two gears: the one permanently attached to the countershaft, and that gear's mate which is now locked to the output shaft.

Locking the output shaft with a gear is achieved by means of a dog clutch
Dog clutch
A dog clutch is a type of clutch that couples two rotating shafts or other rotating components not by friction but by interference. The two parts of the clutch are designed such that one will push the other, causing both to rotate at the same speed and will never slip.Dog clutches are used where...

 selector. The dog clutch is a sliding selector mechanism which is splined to the output shaft, meaning that its hub has teeth that fit into slots (splines) on the shaft, forcing that shaft to rotate with it. However, the splines allow the selector to move back and forth on the shaft, which happens when it is pushed by a selector fork that is linked to the gear lever. The fork does not rotate, so it is attached to a collar bearing on the selector. The selector is typically symmetric: it slides between two gears and has a synchromesh and teeth on each side in order to lock either gear to the shaft.

Synchromesh

If the teeth, the so-called dog teeth, make contact with the gear, but the two parts are spinning at different speeds, the teeth will fail to engage and a loud grinding sound will be heard as they clatter together. For this reason, a modern dog clutch in an automobile has a synchronizer mechanism or synchromesh, which consists of a cone clutch and blocking ring. Before the teeth can engage, the cone clutch
Cone clutch
A cone clutch serves the same purpose as a disk or plate clutch. However, instead of mating two spinning disks, the cone clutch uses two conical surfaces to transmit torque by friction....

 engages first which brings the selector and gear to the same speed using friction. Moreover, until synchronization occurs, the teeth are prevented from making contact, because further motion of the selector is prevented by a blocker (or baulk) ring. When synchronization occurs, friction on the blocker ring is relieved and it twists slightly, bringing into alignment certain grooves and notches that allow further passage of the selector which brings the teeth together. Of course, the exact design of the synchronizer varies from manufacturer to manufacturer.

The synchronizer has to overcome the momentum of the entire input shaft and clutch disk when it is changing shaft rpm to match the new gear ratio. It can be abused by exposure to the momentum and power of the engine itself, which is what happens when attempts are made to select a gear without fully disengaging the clutch. This causes extra wear on the rings and sleeves, reducing their service life. When an experimenting driver tries to "match the revs" on a synchronized transmission and force it into gear without using the clutch, the synchronizer will make up for any discrepancy in RPM. The success in engaging the gear without clutching can deceive the driver into thinking that the RPM of the layshaft and transmission were actually exactly matched. Nevertheless, approximate rev. matching with clutching can decrease the general change between layshaft and transmission and decrease synchro wear.

Reverse

The previous discussion normally applies only to the forward gears. The implementation of the reverse gear is usually different, implemented in the following way to reduce the cost of the transmission. Reverse is also a pair of gears: one gear on the countershaft and one on the output shaft. However, whereas all the forward gears are always meshed together, there is a gap between the reverse gears. Moreover, they are both attached to their shafts: neither one rotates freely about the shaft. What happens when reverse is selected is that a small gear, called an idler gear or reverse idler, is slid between them. The idler has teeth which mesh with both gears, and thus it couples these gears together and reverses the direction of rotation without changing the gear ratio.

In other words, when reverse gear is selected, it is in fact actual gear teeth that are being meshed, with no aid from a synchronization mechanism. For this reason, the output shaft must not be rotating when reverse is selected: the car must be stopped. In order that reverse can be selected without grinding even if the input shaft is spinning inertially, there may be a mechanism to stop the input shaft from spinning. The driver brings the vehicle to a stop, and selects reverse. As that selection is made, some mechanism in the transmission stops the input shaft. Both gears are stopped and the idler can be inserted between them. There is a clear description of such a mechanism in the Honda Civic
Honda Civic
The Honda Civic is a line of subcompact and subsequently compact cars made and manufactured by Honda. The Civic, along with the Accord and Prelude, comprised Honda's vehicles sold in North America until the 1990s, when the model lineup was expanded...

 1996-1998 Service Manual, which refers to it as a "noise reduction system":
A reverse gear implemented this way makes a loud whining sound, which is not normally heard in the forward gears. The teeth on the forward gears of most consumer automobiles are helically cut. When helical gears rotate, there is constant contact between gears, which results in quiet operation. In spite of all forward gears being always meshed, they do not make a sound that can be easily heard above the engine noise. By contrast, most reverse gears are spur gear
Gear
A gear is a rotating machine part having cut teeth, or cogs, which mesh with another toothed part in order to transmit torque. Two or more gears working in tandem are called a transmission and can produce a mechanical advantage through a gear ratio and thus may be considered a simple machine....

s, meaning that they have straight teeth, in order to allow for the sliding engagement of the idler, which is difficult with helical gears. The teeth of spur gears clatter together when the gears spin, generating a characteristic whine.

It is clear that the spur gear design of reverse gear represents some compromises (less robust, unsynchronized engagement and loud noise) which are acceptable due to the relatively small amount of driving that takes place in reverse. The gearbox of the classic SAAB 900
Saab 900
The Saab 900 was a car produced by Saab Automobile from 1978 until 1998 in two generations. The first generation from 1978 to 1993 is known as the "classic"; the generation from 1994 to 1998 is known as the "new generation" ....

 is a notable example of a gearbox with a helical reverse gear engaged in the same unsynchronized manner as the spur gears described above. Its strange design allows reverse to share cogs with first gear, and is exceptionally quiet, but results in difficult engagement and unreliable operation. However, many modern transmissions now include a reverse gear synchronizer and helical gearing.

Ratio count

Until the mid-1970s, cars were generally equipped with 3-speed transmissions as standard equipment. 4-speed units began to appear on volume-production models in the 1950s and gained popularity in the 1960s; some exotics had 5-speeds. In the 1970s, as fuel prices rose and fuel economy became an important selling feature, 4-speed transmissions with an overdrive 4th gear or 5-speeds were offered in mass market automobiles and even compact pickup trucks, pioneered by Toyota (who advertised the fact by giving each model the suffix SR5 as it acquired the fifth speed). 6-speed transmissions started to emerge in high-performance vehicles in the early 1990s.

Today, mass market automotive manual transmissions are nearly all 6-speeds with 5-speed transmissions available in smaller vehicles and entry-level models. Recently Porsche
Porsche
Porsche Automobil Holding SE, usually shortened to Porsche SE a Societas Europaea or European Public Company, is a German based holding company with investments in the automotive industry....

 announced the next-generation 911
Porsche 911
The Porsche 911 is a luxury 2-door sports coupe made by Porsche AG of Stuttgart, Germany. It has a distinctive design, rear-engined and with independent rear suspension, an evolution of the swing axle on the Porsche 356. The engine was also air-cooled until the introduction of the Type 996 in 1998...

 will be available with a 7-speed manual transmission, the first of its kind for a normal automobile with the first six gear ratios the same as the 6-speed gearbox and the 7th gear being of a higher ratio.

Initially the Tesla Roadster
Tesla Roadster
The Tesla Roadster is a battery electric vehicle sports car produced by the electric car firm Tesla Motors in California. The Roadster was the first highway-capable all-electric vehicle in serial production available in the United States. Since 2008 Tesla has sold 2,024 Roadsters in 30 countries...

 was intended to have a purpose-built two-speed manual transmission but this gearbox proved to be problematic and was later replaced with a fixed-ratio transmission.

External overdrive

In the 1950s, '60s, and '70s, fuel-efficient highway cruising with low engine speed was in some cases enabled on cars equipped with 3- or 4-speed transmissions by means of a separate overdrive
Overdrive (mechanics)
Overdrive is a term used to describe a mechanism that allows an automobile to cruise at sustained speed with reduced engine RPM, leading to better fuel economy, lower noise and lower wear...

 unit in or behind the rear housing of the transmission. This was actuated either manually while in high gear by throwing a switch or pressing a button on the gearstick knob or on the steering column, or automatically by momentarily lifting the foot from the accelerator with the car travelling above a certain road speed. Automatic overdrives were disengaged by flooring the accelerator, and a lockout control was provided to enable the driver.

Shaft and gear configuration

On a conventional rear-drive transmission, there are three basic shafts; the input, the output, and the countershaft. The input and output together are called the mainshaft, since they are joined inside the transmission so they appear to be a single shaft, although they rotate totally independently of each other. The input length of this shaft is much shorter than the output shaft. Parallel to the mainshaft is the countershaft. There are a number of gears fixed along the countershaft, and matching gears along the output shaft, although these are not fixed, and rotate independently of the output shaft. There are sliding dog collars, or dog clutches, between the gears on the output shaft, and to engage a gear to the shaft, the collar slides into the space between the shaft and the inside space of the gear, thus rotating the shaft as well. One collar is usually mounted between two gears, and slides both ways to engage one or the other gears, so on a four-speed there would be two collars. A front-drive transmission is basically the same, but may be simplified. There often are two shafts, the input and the output, but depending on the direction of rotation of the engine, three may be required. Rather than the input shaft driving the countershaft with a pinion gear, the input shaft takes over the countershaft's job, and the output shaft runs parallel to it. The gears are positioned and engaged just as they are on the countershaft and output shaft of a rear-drive. This merely eliminates one major component, the pinion gear. Part of the reason that the input and output are in-line on a rear drive unit is to relieve torsional stress on the transmission and mountings, but this isn't an issue in a front-drive as the gearbox is integrated into the transaxle.

The basic process is not universal. The fixed and free gears can be mounted on either the input or output shaft, or both.

The distribution of the shifters is also a matter of design; it need not be the case that all of the free-rotating gears with selectors are on one shaft, and the permanently splined gears on the other. For instance a five-speed transmission might have the first-to-second selectors on the countershaft, but the third-to-fourth selector and the fifth selector on the mainshaft, which is the configuration in the 1998 Honda Civic
Honda Civic
The Honda Civic is a line of subcompact and subsequently compact cars made and manufactured by Honda. The Civic, along with the Accord and Prelude, comprised Honda's vehicles sold in North America until the 1990s, when the model lineup was expanded...

. This means that when the car is stopped and idling in neutral with the clutch engaged and the input shaft spinning, the third, fourth and fifth gear pairs do not rotate.

In some transmission designs (Volvo 850 and V/S70 series, for example) there are actually two countershafts, both driving an output pinion meshing with the front-wheel-drive transaxle's ring gear. This allows the transmission designer to make the transmission narrower, since each countershaft need only be half as long as a traditional countershaft with four gears and two shifters.

Clutch

In all vehicles using a transmission (virtually all modern vehicles), a coupling device is used to separate the engine and transmission when necessary. This is because an internal-combustion engine has to continue to run when it's in use; it essentially can't be stopped when the wheels stop, although a few modern cars with automatic transmissions shut off the engine at a stoplight. The clutch
Clutch
A clutch is a mechanical device which provides for the transmission of power from one component to another...

 accomplishes this in manual transmissions. Without it, the engine and tires would at all times be inextricably linked, and any time the vehicle stopped the engine would stall. Without the clutch, changing gears would be very difficult, even with the vehicle moving already: deselecting a gear while the transmission is under load requires considerable force (and risks significant damage). As well, selecting a gear requires the revolution speed of the engine to be held at a very precise value which depends on the vehicle speed and desired gear – the speeds inside the transmission have to match. In a car the clutch is usually operated by a pedal
Automobile pedal
An automobile may have two to four foot pedals. The arrangement is the same for both right- and left-hand traffic. From left to right:* normally operated by the left foot:**clutch pedal, not in the case of automatic transmission...

; on a motorcycle, a lever on the left handlebar serves the purpose.
  • When the clutch pedal is fully depressed, the clutch is fully disengaged, and no torque
    Torque
    Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....

     is transferred from the engine to the transmission (and by extension to the drive wheels). In this uncoupled state it is possible to select gears or to stop the car without stopping the engine.
  • When the clutch pedal is fully released, the clutch is fully engaged and all of the engine's torque is transferred. In this coupled state, the clutch does not slip, but rather acts as rigid coupling to transmit power to gearbox.
  • Between these extremes of engagement and disengagement the clutch slips to varying degrees. When slipping it still transmits torque despite the difference in speeds between the engine crankshaft and the transmission input. Because this torque is transmitted by means of friction rather than direct mechanical contact, considerable power is wasted as heat (which is dissipated by the clutch). Properly applied, slip allows the vehicle to be started from a standstill, and when it is already moving, allows the engine rotation to gradually adjust to a newly selected gear ratio.
  • Learning to use the clutch efficiently requires the development of muscle memory
    Muscle memory
    Muscle memory has been used synonymously with motor learning, which is a form of procedural memory that involves consolidating a specific motor task into memory through repetition. When a movement is repeated over time, a long-term muscle memory is created for that task, eventually allowing it to...

     and a level of coordination.
  • A rider of a highly tuned motocross or off-road motorcycle may "hit" or "fan" the clutch when exiting corners to assist the engine in revving to the point where it delivers the most power.


The clutch is typically disengaged by a thrust bearing
Thrust bearing
A thrust bearing is a particular type of rotary bearing. Like other bearings they permit rotation between parts, but they are designed to support a high axial load while doing this.Thrust bearings come in several varieties....

 that makes contact with pressure petals on the clutch ring plate and pushes them inward to release the clutch pad friction. Normally the bearing remains retracted away from the petals and does not spin. However, the bearing can be "burned out" and damaged by using the clutch pedal as a foot rest, which causes the bearing to spin continuously from touching the clutch plates.

Floor-mounted shifter

In most vehicles with manual transmission, gears are selected by manipulating a lever called a gear stick, shift stick, gearshift, gear lever, gear selector, or shifter connected to the transmission via linkage or cables
Bowden cable
A Bowden cable is a type of flexible cable used to transmit mechanical force or energy by the movement of an inner cable relative to a hollow outer cable housing...

 and mounted on the floor, dashboard, or steering column. Moving the lever forward, backward, left, and right into specific positions selects particular gears.

A sample layout of a four-speed transmission is shown below. N marks neutral, the position wherein no gears are engaged and the engine is decoupled from the vehicle's drive wheels. The entire horizontal line is a neutral position, though the shifter is usually spring-loaded
Spring (device)
A spring is an elastic object used to store mechanical energy. Springs are usually made out of spring steel. Small springs can be wound from pre-hardened stock, while larger ones are made from annealed steel and hardened after fabrication...

 so it will return to the centre of the N position if not moved to another gear. The R marks reverse, the gear position used for moving the vehicle rearward.



This layout is called the shift pattern. Because of the shift quadrants, the basic arrangement is often called an H-pattern. The shift pattern is usually molded or printed on or near the gear knob. While the layout for gears one through four is nearly universal, the location of reverse is not. Depending on the particular transmission design, reverse may be located at the upper left extent of the shift pattern, at the lower left, at the lower right, or at the upper right. There is often a mechanism that allows selection of reverse only from the neutral position, or a reverse lockout that must be released by depressing the spring-loaded gear knob or lifting a spring-loaded collar on the shift stick, to reduce the likelihood of the driver inadvertently selecting reverse.

"Four on the floor"

Four-speed transmissions with floor-mounted shifters were sometimes referred to as "four on the floor" during the period when the steering column was the more common shifter location. The latter, often being the standard non-performance transmission, usually had only three forward speeds and was referred to as "three on the tree."

Most front-engined, rear-wheel drive cars have a transmission that sits between the driver and the front passenger seat. Floor-mounted shifters are often connected directly to the transmission. Front-wheel drive
FF layout
In automotive design, an FF, or Front-engine, Front-wheel drive layout places both the internal combustion engine and driven roadwheels at the front of the vehicle.-Usage implications:...

 and rear-engined
RR layout
In automotive design, a RR, or Rear-engine, Rear-wheel drive layout places both the engine and drive wheels at the rear of the vehicle. In contrast to the RMR layout, the center of mass of the engine is between the rear axle and the rear bumper....

 cars often require a mechanical linkage to connect the shifter to the transmission.

Column-mounted shifter

Some cars have a gear lever mounted on the steering column of the car. A 3-speed column shifter, which came to be popularly known as a "Three on the Tree", began appearing in America in the late 1930s and became common during the 1940s and '50s. If a U.S. vehicle was equipped with overdrive, it was very likely to be a Borg-Warner type, operated by briefly backing off the gas when above 28 mph to enable, and momentarily flooring the gas pedal to return to normal gear. The control simply disables overdrive for such situations as parking on a hill or preventing unwanted shifting into overdrive.(Scroll down to "Overdrive In North America".)



Later, European and Japanese models began to have 4-speed column shifters with this shift pattern:



The column-mounted manual shifter disappeared in North America by the mid 1980s, last appearing in the 1987 Chevrolet pickup truck. Outside North America, the column-mounted shifter remained in production. All Toyota Crown
Toyota Crown
The Toyota Crown is a line of full-size luxury sedans by Toyota. The range was primarily available in Japan and some other Asian countries, originally designed to serve as a taxi...

 and Nissan Cedric
Nissan Cedric
The Nissan Cedric is a large automobile produced by Nissan since 1960. It was developed to provide upscale transportation, competing with the Prince Skyline and Gloria which were later merged into the Nissan family...

 taxis in Hong Kong
Taxicabs of Hong Kong
Taxicabs of Hong Kong provide a taxi system. Most taxis are independently owned and operated, but some are owned by taxi companies, and the drivers are employees....

 had the 4-speed column shift until 1999 when automatic transmissions were first offered. Since the late 1980s or early 1990s, a 5-speed column shifter has been offered in some vans sold in Asia and Europe, such as Toyota Hiace
Toyota Hiace
The Toyota HiAce is a motor vehicle produced by the Japanese manufacturer Toyota. First launched in 1967, the HiAce has since been available in a wide range of configurations, including minivan and minibus, van, pick-up, taxi, and ambulance....

 and Mitsubishi L400
Mitsubishi Delica
The Mitsubishi Delica is a range of trucks and multi-purpose vehicles built by Mitsubishi Motors since 1968. It was originally based on a small pickup truck introduced the previous year, also called the Delica, its name a contraction of the English language phrase Delivery car...

.

Column shifters are mechanically similar to floor shifters, although shifting occurs in a vertical plane instead of a horizontal one. Because the shifter is further away from the transmission, and the movements at the shifter and at the transmission are in different planes, column shifters require more complicated linkage
Linkage
Linkage generally means "the manner or style of being united", and can refer to:*Genetic linkage, the tendency of certain genes to be inherited together*Flux linkage, the total flux passing through a surface formed by a closed conducting loop...

 than floor shifters. Advantages of a column shifter are the ability to switch between the two most commonly used gears—second and third—without letting go of the steering wheel, and the lack of interference with passenger seating space in vehicles equipped with a bench seat
Bench seat
The bench seat was the traditional seat installed in American automobiles. This seat featured a continuous pad running the full width of the cabin...

.

Console-mounted shifter

Newer small cars and MPV
Minivan
Minivan is a type of van designed for personal use. Minivans are typically either two-box or one box designs for maximum interior volume – and are taller than a sedan, hatchback, or a station wagon....

s, like the Suzuki MR Wagon
Suzuki MR Wagon
The Suzuki MR Wagon is a kei car with a mini MPV body, seating four, manufactured by Suzuki for the Japanese market only, and also marketed in Japan by Nissan as the Nissan Moco under an OEM agreement. The model debuted in 2001, and since 2007 it has been in its second generation...

, the Fiat Multipla
Fiat Multipla
The Fiat Multipla is a compact MPV manufactured by Italian automaker Fiat since 1998. Based on the Brava, the Multipla is shorter and wider than its rivals. It has two rows of three seats, while all its competitors have two seats in the front...

, the Toyota Matrix
Toyota Matrix
The Toyota Matrix, sometimes officially referred to as the Toyota Corolla Matrix, is a compact hatchback manufactured by the Toyota Motor Corporation in Canada, to be sold in the United States, Canada, and Mexico...

, the Pontiac Vibe
Pontiac Vibe
The Pontiac Vibe is a compact hatchback car that was produced in Fremont, California, in the United States by NUMMI , a joint venture between General Motors and Toyota, and marketed under General Motors' Pontiac brand...

, the Chrysler RT platform cars and the Honda Civic Si
Honda Civic Si
The Honda Civic Si is a sport compact / hot hatch version of the Civic built by the Japanese automaker Honda. The Si trim, which stands for "Sport Injected," was introduced for the third generation of Honda Civics in both Japan and North America...

 EP3 may feature a manual or automatic transmission
Automatic transmission
An automatic transmission is one type of motor vehicle transmission that can automatically change gear ratios as the vehicle moves, freeing the driver from having to shift gears manually...

 gear shifter located on the vehicle's instrument panel. Console-mounted shifters are similar to floor-mounted gear shifters in that most of the ones used in modern cars operate on a horizontal plane and can be mounted to the vehicle's transmission in much the same way a floor-mounted shifter can. However, because of the location of the gear shifter in comparison to the locations of the column shifter and the floor shifter, as well as the positioning of the shifter to the rest of the controls on the panel often require that the gearshift be mounted in a space that does not feature a lot of controls integral to the vehicle's operation or frequently used controls, such as those for the car stereo or car air conditioning, to help prevent accidental activation or driver confusion, especially in right-hand drive cars.

More and more small cars and vans from manufacturers such as Suzuki
Suzuki
is a Japanese multinational corporation headquartered in Hamamatsu, Japan that specializes in manufacturing compact automobiles and 4x4 vehicles, a full range of motorcycles, all-terrain vehicles , outboard marine engines, wheelchairs and a variety of other small internal combustion engines...

, Honda
Honda
is a Japanese public multinational corporation primarily known as a manufacturer of automobiles and motorcycles.Honda has been the world's largest motorcycle manufacturer since 1959, as well as the world's largest manufacturer of internal combustion engines measured by volume, producing more than...

, and Volkswagen
Volkswagen
Volkswagen is a German automobile manufacturer and is the original and biggest-selling marque of the Volkswagen Group, which now also owns the Audi, Bentley, Bugatti, Lamborghini, SEAT, and Škoda marques and the truck manufacturer Scania.Volkswagen means "people's car" in German, where it is...

 are featuring console shifters in that they free up space on the floor for other car features such as storage compartments without requiring that the gear shift be mounted on the steering column. Also, the basic location of the gear shift in comparison to the column shifter makes console shifters easier to operate than column shifters.

Sequential manual

Some transmissions do not allow the driver to arbitrarily select any gear. Instead, the driver may only ever select the next-lowest or next-highest gear ratio. Sequential transmissions often incorporate a synchro-less dog-clutch engagement mechanism (instead of the synchromesh dog clutch common on H-pattern automotive transmissions), in which case the clutch is only necessary when selecting first or reverse gear from neutral, and most gear changes can be performed without the clutch. However, sequential shifting and synchro-less engagement are not inherently linked, though they often occur together due to the environment(s) in which these transmissions are used, such as racing cars and motorcycles.

Sequential transmissions are generally controlled by a forward-backward lever, foot pedal, or set of paddles mounted behind the steering wheel. In some cases, these are connected mechanically to the transmission. In many modern examples, these controls are attached to sensors which instruct a transmission computer to perform a shift—many of these systems can be switched into an automatic mode, where the computer controls the timing of shifts, much like an automatic transmission
Automatic transmission
An automatic transmission is one type of motor vehicle transmission that can automatically change gear ratios as the vehicle moves, freeing the driver from having to shift gears manually...

.

Motorcycles typically employ sequential transmissions, although the shift pattern is modified slightly for safety reasons. In a motorcycle the gears are usually shifted with the left foot pedal, the layout being this:
6 - 5 - 4 - 3 - 2 N 1

The pedal goes one step–both up and down–from the center, before it reaches its limit and has to be allowed to move back to the center position. Thus, changing multiple gears in one direction is accomplished by repeatedly pumping the pedal, either up or down. Although neutral is listed as being between first and second gears for this type of transmission, it "feels" more like first and second gear are just "further away" from each other than any other two sequential gears. Because this can lead to difficulty in finding neutral for inexperienced riders most motorcycles have a neutral indicator light on the instrument panel to help find neutral. The reason neutral does not actually have its own spot in the sequence is to make it quicker to shift from first to second when moving. Neutral can be accidentally shifted into, though most high end, newer model motorcycles have means of avoiding this. The reason for having neutral between the first and second gears instead of at the bottom is that when stopped, the rider can just click down repeatedly and know that they will end up in first and not neutral. This allows a rider to quickly move his bike from a standstill in an emergency situation. This may also help on a steep hill on which high torque is required. It could be disadvantageous or even dangerous to attempt to be in first without realizing it, then try for a lower gear, only to get neutral.

On motorcycles used on race tracks, the shifting pattern is often reversed, that is, the rider clicks down to upshift. This usage pattern increases the ground clearance by placing the riders foot above the shift lever when the rider is most likely to need it, namely when leaning over and exiting a tight turn.

The shift pattern for most underbone
Underbone
An underbone is a small motorcycle built on a frame consisting mostly of one large diameter tubular component.The stylistic difference between a motorcycle and an underbone is considerable and they are sometimes known as "step-throughs" or even marketed as scooters in the West.The fuel tank...

 motorcycles with an automatic centrifugal clutch
Centrifugal clutch
A centrifugal clutch is a clutch that uses centrifugal force to connect two concentric shafts, with the driving shaft nested inside the driven shaft....

 is also modified for two key reasons - to enable the less-experienced riders to shift the gears without problems of "finding" neutral, and also due to the greater force needed to "lift" the gearshift lever (because the gearshift pedal of an underbone motorcycle also operates the clutch). The gearshift lever of an underbone motorcycle has two ends. The rider clicks down the front end with the left toe all the way to the top gear and clicks down the rear end with the heel all the way down to neutral. Some underbone models such as the Honda Wave
Honda Wave series
Honda Wave series, also known as Honda NF series, Honda Innova , and Honda Supra is a series of small motorcycles the underbone type, manufactured by Honda Motor Co. Ltd as a successor of the Honda Cub series. It debuted in 1995 especially for Asian and European market...

 have a "rotary" shift pattern, which means that the rider can shift directly to neutral from the top gear, but for safety reasons this is only possible when the motorcycle is stationary. Some models also have gear position indicators for all gear positions at the instrument panel.

Semi-manual

Some new transmissions (Alfa Romeo
Alfa Romeo
Alfa Romeo Automobiles S.p.A. is an Italian manufacturer of cars. Founded as A.L.F.A. on June 24, 1910, in Milan, the company has been involved in car racing since 1911, and has a reputation for building expensive sports cars...

's Selespeed
Selespeed
Selespeed is the name of an electrohydraulic manual transmission used in Alfa Romeo cars, developed by Italian company Magneti Marelli. The Selespeed is a robotized manual gearbox with electronic clutch. In its current incarnation it can be operated via paddle shifters from the steering wheel or...

 gearbox and BMW
BMW
Bayerische Motoren Werke AG is a German automobile, motorcycle and engine manufacturing company founded in 1916. It also owns and produces the Mini marque, and is the parent company of Rolls-Royce Motor Cars. BMW produces motorcycles under BMW Motorrad and Husqvarna brands...

's Sequential Manual Gearbox (SMG) for example) are conventional manual transmissions with a computerized control mechanism. These transmissions feature independently selectable gears but do not have a clutch
Clutch
A clutch is a mechanical device which provides for the transmission of power from one component to another...

 pedal. Instead, the transmission computer controls a servo
Servomechanism
thumb|right|200px|Industrial servomotorThe grey/green cylinder is the [[Brush |brush-type]] [[DC motor]]. The black section at the bottom contains the [[Epicyclic gearing|planetary]] [[Reduction drive|reduction gear]], and the black object on top of the motor is the optical [[rotary encoder]] for...

 which disengages the clutch when necessary.

These transmissions vary from sequential transmissions in that they still allow nonsequential shifts: BMWs SMG system, for example, can shift from 6th gear directly to 4th gear.

In the case of the early second generation Saab 900, a 'Sensonic' option was available where gears were shifted with a conventional shifter, but the clutch is controlled by a computer.

Fuel economy

The manual transmission couples the engine to the transmission with a rigid clutch instead of the torque converter
Torque converter
In modern usage, a torque converter is generally a type of hydrodynamic fluid coupling that is used to transfer rotating power from a prime mover, such as an internal combustion engine or electric motor, to a rotating driven load...

 on an automatic transmission or the v-belt of a continuously variable transmission, which slip by nature. Manual transmissions also lack the parasitic power consumption of the automatic transmission's hydraulic pump. Because of this, manual transmissions generally offer better fuel economy
Fuel economy
Fuel economy may refer to:*Fuel economy in automobiles, refers to the fuel efficiency relationship between distance traveled by an automobile and the amount of fuel consumed*Fuel efficiency in general...

 than automatic or continuously variable transmissions; however the disparity has been somewhat offset with the introduction of locking torque converters on automatic transmissions. Increased fuel economy with a properly operated manual transmission vehicle versus an equivalent automatic transmission vehicle can range from 5% to about 15% depending on driving conditions and style of driving. The lack of control over downshifting under load in an automatic transmission, coupled with a typical vehicle engine's greater efficiency under higher load, can enable additional fuel gains from a manual transmission by allowing the operator to keep the engine performing under a more efficient load/RPM combination. Also, manual transmissions do not require active cooling and because they are, mechanically, much simpler than automatic transmissions, they generally weigh less than comparable automatics, which can improve economy in stop-and-go traffic.

Longevity and cost

Because manual transmissions are mechanically simpler and have fewer moving parts than automatic transmissions, they require less maintenance and are easier to repair. This is one of the many reasons manual transmissions are still offered today, and why the demand for them still has a place in the market. The price of a new car with a manual transmission will often be lower than the same car with an automatic transmission.

Performance and control

Manual transmissions generally offer a wider selection of gear ratios. Many vehicles offer a 5-speed or 6-speed manual, whereas the automatic option would typically be a 4-speed. This is generally due to the increased space available inside a manual transmission compared with an automatic, since the latter requires extra components for self-shifting, such as torque converters and pumps. However, automatic transmissions are now adding more speeds as the technology matures. ZF currently makes 7- and 8-speed automatic transmissions. The increased number gears allows for better use of the engine's power band
Power band
The power band of an engine or electric motor refers to the range of operating speeds under which an the engine or motor is able to operate efficiently...

, allowing increased fuel economy, by staying in the most fuel-efficient part of the power band, or higher performance, by staying closer to the engine's peak power.

Because the driver has more direct control over the car with a manual than with an automatic, an experienced, knowledgeable driver who knows the correct procedure for executing a driving maneuver, and wants the vehicle to realize his or her intentions exactly and instantly, can perform actions difficult or impossible with automatic transmissions. When starting forward, for example, the driver can control how much torque goes to the tires, which is useful on slippery surfaces such as ice, snow or mud. This can be done with clutch finesse, or by starting in second gear instead of first. However, some automatic transmissions, particularly those with tiptronic gear selectors, can be placed in second gear for starting on slippery surfaces. An engine coupled with a manual transmission can often be started by the method of push start
Push start
Push starting, also known as bump starting, pop starting or crash starting is a method of starting a motor vehicle with an internal combustion engine by engaging the manual transmission through the motion of the vehicle...

ing. This is particularly useful if the starter
Automobile self starter
A starter motor is an electric motor for rotating an internal-combustion engine so as to initiate the engine's operation under its own power.- History :...

 is inoperable or defunct, or the battery has drained below operable voltage. Similarly, a vehicle with a manual transmission and no clutch/starter interlock switch can be moved, if necessary, by cranking the starter while in gear. This is useful when the vehicle will not start but must be immediately moved, e.g. off the road in the event of a breakdown, if the vehicle has stalled on a railway crossing, or in extreme off-roading cases such as an engine that has stalled in deep water.

Engine braking

In contrast to most manual gearboxes, most automatic transmissions have a free-wheel-clutch. This means that the engine does not slow down the car when the driver steps off the throttle, also known as engine or compression braking. This leads to more usage of the brakes in cars with automatic transmissions, which can potentially overheat them in hilly or mountainous areas, causing reduced braking ability and the potential for complete failure. However, the automatic gearboxes in commodity Nissans and Hondas disable the free wheel operation completely if the driver has selected a gear position other than "D" - either "1", "2", or "D with overdrive off". This works by blocking the free-wheel sprag using a multi-disk clutch called the "overrun clutch". Similarly, many trucks have a "tow mode" that allows engine braking.

Complexity and learning curve

There is a significant learning curve
Learning curve
A learning curve is a graphical representation of the changing rate of learning for a given activity or tool. Typically, the increase in retention of information is sharpest after the initial attempts, and then gradually evens out, meaning that less and less new information is retained after each...

 with a manual transmission, and the smoothness and correct timing of gear shifts are wholly dependent on the driver's experience and skill. Because the driver must develop a feel for properly engaging the clutch, especially when starting forward on a steep road or when parking on an incline, an inexperienced driver can easily stall the engine, or cause the car to jerk and bounce abruptly, which is not only uncomfortable, but could potentially be dangerous in an area with little room for error. Additionally, if an inexperienced driver selects the wrong gear by mistake, they can do damage to the engine and/or transmission. Selecting too high a gear can "lug" the motor, lowering the lifespan over time, while selecting too low a gear for the speed of the car can over-rev the engine, causing severe damage very quickly.

Attempting to select reverse while the vehicle is moving forward causes severe gear wear (except in transmissions with synchromesh on the reverse gear). However, most manual transmissions have a gate that locks out reverse directly from 5th gear to help prevent this. In order to engage reverse from 5th, the shift lever has to be moved to the center position between 2nd and 3rd, then back over and into reverse. Similarly, many newer six-speed manual transmissions have a collar under the shift knob which must be lifted to engage reverse to also help prevent this.

Shifting speed

Some automatic transmissions can shift ratios faster than a manual gear change can be accomplished, due to the time required for the average driver to push the clutch pedal to the floor and move the gearstick from one position to another. This is especially true in regards to dual clutch transmission
Dual clutch transmission
A dual clutch transmission, commonly abbreviated to DCT , is a differing type of semi-automatic or automated manual automotive transmission. It utilises two separate clutches for odd and even gear sets...

s, which are specialized computer-controlled manual transmissions. Even though some automatic transmissions and semi-automatic transmissions can shift faster, many purists still prefer a regular manual transmission.

Ease of use

Because manual transmissions require the operation of an extra pedal, and keeping the car in the correct gear at all times, they require a bit more concentration, especially in heavy traffic situations. The automatic transmissions, on the other hand, simply require the driver to speed up or slow down as needed, with the car doing the work of choosing the correct gear. Manual transmissions also place a greater workload on the driver in heavy traffic situations, when the driver must operate the clutch pedal quite often. Because the clutch pedal can require a substantial amount of force, especially on large trucks, and the long pedal travel compared to the brake or accelerator requires moving the entire leg, not just the foot near the ankle, a manual transmission can cause fatigue, and is more difficult for weak or injured people to drive. Additionally, because automatic transmissions can be driven with only one foot, people with one leg that is missing or impaired can still drive, unlike the manual transmission that requires the use of two feet at once. Likewise, manual transmissions require the driver to remove one hand periodically from the steering wheel while the vehicle is in motion, which can be difficult or impossible to do safely for people with a missing or impaired arm, and requires increased coordination, even for those with full use of both hands.

Stopping on hills

The clutch experiences most of its wear in first gear because moving the car from a standstill involves a great deal of friction at the clutch. When accelerating from a standstill on an incline, this problem is made worse because the amount of work needed to overcome the acceleration of gravity causes the clutch to heat up considerably more. For this reason, stop-and-go driving and hills tend to wear out clutches very quickly. Automatic transmissions are better suited for these applications because they have a hydraulic torque converter which is externally cooled, unlike a clutch. Torque converters also do not have a friction material that rubs off over time like a clutch. Some automatics even lock the output shaft so that the car cannot roll backwards when beginning to accelerate up an incline. To reduce wear in these applications, some manual transmissions will have a very low, "granny" gear which provides the leverage to move the vehicle easily at very low speeds. This reduces wear at the clutch because the transmission requires less input torque.

Many drivers use the parking brake to prevent the car from rolling backward when starting to accelerate up a steep hill. This saves precious clutch life.

Applications and popularity

Many types of automobiles are equipped with manual transmissions.

Sports cars are also often equipped with manual transmissions because they offer more direct driver involvement and better performance. Off-road vehicles and trucks often feature manual transmissions because they allow direct gear selection and are often more rugged than their automatic counterparts.

Conversely, manual transmissions are no longer popular in many classes of cars sold in North America, Australia and some parts of Asia, although they remain dominant in Europe, Asia and developing countries. Nearly all cars are available with an automatic transmission option, and family cars and large trucks sold in the US are predominantly fitted with automatics, however in some cases if a buyer wishes he/she can have the car fitted with a manual transmission at the factory. In Europe most cars are sold with manual transmissions. Most luxury cars are only available with an automatic transmission. In most cases where both transmissions are available for a given car, automatics are an at cost option, but in some cases the reverse is true. Some cars, such as rental cars and taxi
Taxicab
A taxicab, also taxi or cab, is a type of vehicle for hire with a driver, used by a single passenger or small group of passengers, often for a non-shared ride. A taxicab conveys passengers between locations of their choice...

s, are nearly universally equipped with automatic transmissions in countries such as the US, but the opposite is true in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

. As of 2008, 75.2% of vehicles made in Western Europe were equipped with manual transmission, versus 16.1% with automatic and 8.7% with other.

In some places (for example New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

 (for the second-phase Restricted licence, but not the final Full licence), Belgium
Belgium
Belgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...

, China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

, Estonia
Estonia
Estonia , officially the Republic of Estonia , is a state in the Baltic region of Northern Europe. It is bordered to the north by the Gulf of Finland, to the west by the Baltic Sea, to the south by Latvia , and to the east by Lake Peipsi and the Russian Federation . Across the Baltic Sea lies...

, Dominican Republic
Dominican Republic
The Dominican Republic is a nation on the island of La Hispaniola, part of the Greater Antilles archipelago in the Caribbean region. The western third of the island is occupied by the nation of Haiti, making Hispaniola one of two Caribbean islands that are shared by two countries...

, Finland
Finland
Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...

, France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

, Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

, Ireland
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...

, Israel
Israel
The State of Israel is a parliamentary republic located in the Middle East, along the eastern shore of the Mediterranean Sea...

, Jordan
Jordan
Jordan , officially the Hashemite Kingdom of Jordan , Al-Mamlaka al-Urduniyya al-Hashemiyya) is a kingdom on the East Bank of the River Jordan. The country borders Saudi Arabia to the east and south-east, Iraq to the north-east, Syria to the north and the West Bank and Israel to the west, sharing...

, Netherlands
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...

, Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

, Poland
Poland
Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...

, Singapore
Singapore
Singapore , officially the Republic of Singapore, is a Southeast Asian city-state off the southern tip of the Malay Peninsula, north of the equator. An island country made up of 63 islands, it is separated from Malaysia by the Straits of Johor to its north and from Indonesia's Riau Islands by the...

, Slovenia
Slovenia
Slovenia , officially the Republic of Slovenia , is a country in Central and Southeastern Europe touching the Alps and bordering the Mediterranean. Slovenia borders Italy to the west, Croatia to the south and east, Hungary to the northeast, and Austria to the north, and also has a small portion of...

, South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

, South Korea
South Korea
The Republic of Korea , , is a sovereign state in East Asia, located on the southern portion of the Korean Peninsula. It is neighbored by the People's Republic of China to the west, Japan to the east, North Korea to the north, and the East China Sea and Republic of China to the south...

, Spain
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...

, Sri Lanka
Sri Lanka
Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka is a country off the southern coast of the Indian subcontinent. Known until 1972 as Ceylon , Sri Lanka is an island surrounded by the Indian Ocean, the Gulf of Mannar and the Palk Strait, and lies in the vicinity of India and the...

, Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

, Turkey
Turkey
Turkey , known officially as the Republic of Turkey , is a Eurasian country located in Western Asia and in East Thrace in Southeastern Europe...

, U.A.E and the UK), when a driver takes the licensing road test using an automatic transmission
Automatic transmission
An automatic transmission is one type of motor vehicle transmission that can automatically change gear ratios as the vehicle moves, freeing the driver from having to shift gears manually...

, the resulting license is restricted to the use of automatic transmissions. This treatment of the manual transmission skill seems to maintain the widespread use of the manual transmission. As many new drivers worry that their restricted license will become an obstacle for them where most cars have manual transmissions, they make the effort to learn with manual transmissions and obtain full licenses. Some other countries (such as India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

, Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

, Pakistan
Pakistan
Pakistan , officially the Islamic Republic of Pakistan is a sovereign state in South Asia. It has a coastline along the Arabian Sea and the Gulf of Oman in the south and is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast. In the north, Tajikistan...

, Malaysia, Serbia
Serbia
Serbia , officially the Republic of Serbia , is a landlocked country located at the crossroads of Central and Southeast Europe, covering the southern part of the Carpathian basin and the central part of the Balkans...

, Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

, Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

, Ukraine
Ukraine
Ukraine is a country in Eastern Europe. It has an area of 603,628 km², making it the second largest contiguous country on the European continent, after Russia...

 and Denmark
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...

) go even further, whereby the license is granted only when a test is passed on a manual transmission. In Denmark and Brazil drivers are allowed to take the test on an automatic if they are handicapped, but with such a license they will not be allowed to drive a car with a manual transmission.

Truck transmissions

Some trucks have transmissions that look and behave like ordinary car transmissions - these transmissions are used on lighter trucks, typically have up to 6 gears, and usually have synchromesh.

For trucks needing more gears, the standard "H" pattern can get very complicated, so additional controls are used to select additional gears. The "H" pattern is retained, then an additional control selects among alternatives. In older trucks, the control is often a separate lever mounted on the floor or more recently a pneumatic switch mounted on the "H" lever; in newer trucks the control is often an electrical switch mounted on the "H" lever. Multi-control transmissions are built in much higher power ratings, but rarely use synchromesh.

There are several common alternatives for the shifting pattern. Usual types are:
  • Range transmissions use an "H" pattern through a narrow range of gears, then a "range" control shifts the "H" pattern between high and low ranges. For example, an 8-speed range transmission has an H shift pattern with four gears. The first through fourth gears are accessed when low range is selected. To access the fifth through eighth gears, the range selector is moved to high range, and the gear lever again shifted through the first through fourth gear positions. In high range, the first gear position becomes fifth, the second gear position becomes sixth, and so on.
  • Splitter transmissions use an "H" pattern with a wide range of gears, and the other selector splits each sequential gear position in two: First gear is in first position/low split, second gear is in first position/high split, third gear is in second position/low split, fourth gear is in second position/high split, and so on.
  • Range-Splitter transmissions combine range-splitting and gear-splitting. This allows even more gear ratios. Both a range selector and a splitter selector are provided.


Although there are many gear positions, shifting through gears usually follows a regular pattern. For example, a series of upshifts might use "move to splitter direct; move to splitter overdrive; move shift lever to No. 2 and move splitter to underdrive; move splitter to direct; move splitter to overdrive; move shift lever to No. 3 and move splitter to underdrive"; and so on. In older trucks using floor-mounted levers, a bigger problem is common gear shifts require the drivers to move their hands between shift levers in a single shift, and without synchromesh, shifts must be carefully timed or the transmission will not engage. For this reason, some splitter transmissions have an additional "under under" range, so when the splitter is already in "under" it can be quickly downshifted again, without the delay of a double shift.

Today's truck transmissions are most commonly "range-splitter". The most common 13-speed has a standard H pattern, and the pattern from left upper corner is as follows: R, down to L, over and up to 1, down to 2, up and over to 3, down to 4. The "butterfly" range lever in the center front of the knob is flipped up to high range while in 4th, then shifted back to 1. The 1 through 4 positions of the knob are repeated. Also, each can be split using the thumb-actuated under-overdrive lever on the left side of the knob while in high range. The "thumb" lever is not available in low range, except in 18 speeds; 1 through 4 in low range can be split using the thumb lever and L can be split with the "Butterfly" lever. L cannot be split using the thumb lever in either the 13- or 18-speed. The 9-speed transmission is basically a 13-speed without the under-overdrive thumb lever.

Truck transmissions use many physical layouts. For example, the output of an N-speed transmission may drive an M-speed secondary transmission, giving a total of N*M gear combinations; for example a 4-speed main box and 3-speed splitter gives 12 ratios. Transmissions may be in separate cases with a shaft in between; in separate cases bolted together; or all in one case, using the same lubricating oil. The second transmission is often called a "Brownie" or "Brownie box" after a popular brand. With a third transmission, gears are multiplied yet again, giving greater range or closer spacing. Some trucks thus have dozens of gear positions, although most are duplicates. Sometimes a secondary transmission is integrated with the differential in the rear axle, called a "two-speed rear end." Two-speed differentials are always splitters. In newer transmissions, there may be two countershafts, so each main shaft gear can be driven from one or the other countershaft; this allows construction with short and robust countershafts, while still allowing many gear combinations inside a single gear case.

Heavy-duty transmissions are almost always non-synchromesh
Non-synchronous transmission
A non-synchronous transmission is a form of transmission based on gears that do not use synchronizing mechanisms. They are found primarily in various types of agricultural, and commercial vehicles...

. One argument is synchromesh adds weight that could be payload, is one more thing to fail, and drivers spend thousands of hours driving so can take the time to learn to drive efficiently with a non-synchromesh transmission. Heavy-duty trucks driven frequently in city traffic, such as cement mixers, need to be shifted very often and in stop-and-go traffic. Since few heavy-duty transmissions have synchromesh, automatic transmission
Automatic transmission
An automatic transmission is one type of motor vehicle transmission that can automatically change gear ratios as the vehicle moves, freeing the driver from having to shift gears manually...

s are commonly used instead, despite their increased weight, cost, and loss of efficiency.

Heavy trucks are usually powered with diesel engine
Diesel engine
A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...

s. Diesel truck engines from the 1970s and earlier tend to have a narrow power band, so need many close-spaced gears. Starting with the 1968 Maxidyne, diesel truck engines have increasingly used turbochargers and electronic controls that widen the power band, allowing fewer and fewer gear ratios. A transmission with fewer ratios is lighter and may be more efficient due to fewer transmissions in series. Fewer shifts also makes the truck more drivable. As of 2005, fleet operators often use 9,10,13 or 18-speed transmissions, but automated manual and semi-automatic transmissions are becoming more common on heavy vehicles, as they can improve efficiency and drivability, reduce the barrier to entry for new drivers, and may improve safety by allowing the driver to concentrate on road conditions.

Maintenance

Because clutches use changes in friction
Friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:...

 to modulate the transfer of torque between engine and transmission, they are subject to wear in everyday use. A very good clutch, when used by an expert driver, can last hundreds of thousands of kilometres (or miles). Weak clutches, abrupt downshifting, inexperienced drivers, and aggressive driving can lead to more frequent repair or replacement.

Manual transmissions are lubricated with gear oil or engine oil in some cars, which must be changed periodically in some cars, although not as frequently as the automatic transmission fluid in a vehicle so equipped. (Some manufacturers specify that changing the gear oil is never necessary except after transmission work or to rectify a leak.)

Gear oil has a characteristic aroma due to the addition of sulfur-bearing anti-wear compounds. These compounds are used to reduce the high sliding friction by the helical gear cut of the teeth (this cut eliminates the characteristic whine of straight cut spur gears). On motorcycles with "wet" clutches (clutch is bathed in engine oil), there is usually nothing separating the lower part of the engine from the transmission, so the same oil lubricates both the engine and transmission. The original Mini placed the gearbox in the oil sump below the engine, thus using the same oil for both.


See also

  • Transmission (mechanics)
    Transmission (mechanics)
    A machine consists of a power source and a power transmission system, which provides controlled application of the power. Merriam-Webster defines transmission as: an assembly of parts including the speed-changing gears and the propeller shaft by which the power is transmitted from an engine to a...

    • Non-synchronous transmission
      Non-synchronous transmission
      A non-synchronous transmission is a form of transmission based on gears that do not use synchronizing mechanisms. They are found primarily in various types of agricultural, and commercial vehicles...

    • Toploader Transmission
      Toploader Transmission
      A Toploader transmission is a manually shifted three and four speed gearbox introduced in 1964 by Ford Motor Company to replace the BorgWarner T-10. It was used in most Fords and Mercurys from 1964 until 1973 as well as some foreign models...

    • Borg-Warner T-56
      Borg-Warner T-56
      The T-56 six speed manual transmission has been used in a wide range of vehicles from General Motors, Dodge, and Ford Motor Company. The transmission was originally designed and built by Borg-Warner for the Dodge Viper later being used by GM in 1992 for the generation II and later engines, but as...

    • Automatic transmission
      Automatic transmission
      An automatic transmission is one type of motor vehicle transmission that can automatically change gear ratios as the vehicle moves, freeing the driver from having to shift gears manually...

    • Preselector gearbox
      Preselector gearbox
      A preselector or self-changing gearbox is a type of manual gearbox used on a variety of vehicles, most commonly in the 1930s...

  • Freewheel
    Freewheel
    thumb|Freewheel mechanismIn mechanical or automotive engineering, a freewheel or overrunning clutch is a device in a transmission that disengages the driveshaft from the driven shaft when the driven shaft rotates faster than the driveshaft...

  • Gear ratio
    Gear ratio
    The gear ratio of a gear train is the ratio of the angular velocity of the input gear to the angular velocity of the output gear, also known as the speed ratio of the gear train. The gear ratio can be computed directly from the numbers of teeth of the various gears that engage to form the gear...

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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