Turbo-Hydramatic 125
Encyclopedia
The Turbo-Hydramatic 125 was the first in a line of automatic transmission
s from General Motors designed for transverse engine
application. Introduced in 1980, the line evolved into today's 4T40/45/65/80
line.
The 125 was renamed 3T40 later, following GM's new naming convention. The 4T40-E
replaced it starting in 1995.
Applications:
controlled solenoid
that would engage the torque converter
into "lock up" where engine power was transferred directly to the transaxle. The C comes from the use of a torque converter clutch (TCC). The solenoid that controls this is notorious for failure, their failure is indicated by an engine stall when braking from speeds greater than 55 MPH. This occurs because the clutch does not disengage and the engine cannot produce enough output to keep the vehicle in motion.
A 4-speed version of the 125 was created for the 1985–1986 GM C platform (FWD)/GM H platform (FWD)
cars, the Turbo-Hydramatic 440-T4. Many parts were identical to the 125, though it was generally stronger and included an overdrive
fourth gear. This transmission was first used in GM's 1985 Buick Park Avenue, Oldsmobile 98, and Cadillac Deville. In 1986, after switching to FWD, the Buick LeSabre, Oldsmobile Delta 88, and later, the Pontiac Bonneville also used this transmission. A special strengthened F-7 version was also used for the 1987–1992 Cadillac Allanté
.
One unique feature of this transmission is its use of both a modulator valve and a throttle valve (TV) cable. Most transmissions either use one or the other to control shift points and shift smoothness. On the Turbo 440-T4, the TV cable exclusively controls the shift points, while the modulator valve controls the shift feel. This feature makes it very easy for a home, "shadetree" mechanic to adjust the transmission shift points with minimum effect on the shift feel.
The 440-T4 was originally slated to be used with downsized C body cars for 1984, however, issues with failures led to introduction being delayed until 1984 for the 1985 model year.
The 440-T4 was later renamed the 4T60.
A heavy-duty version of the 4T60 was used for the 1989-1990 Pontiac Turbo Grand Prix.
The electronically-controlled 4T60-E was introduced in 1991. It would become the basis of the GM 4T65 transmission, still used today.
A heavy-duty version of the 4T60-E was used only in 1996 L67 Equipped vehicles.
Applications:
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 from General Motors designed for transverse engine
Transverse engine
A transverse engine is an engine mounted in a vehicle so that the engine's crankshaft axis is perpendicular to the long axis of the vehicle. Many modern front wheel drive vehicles use this engine mounting configuration...
application. Introduced in 1980, the line evolved into today's 4T40/45/65/80
GM 4T40 transmission
The 4T40-E and 4T45-E are a series of automatic transaxles from General Motors. Designed for transverse engine configurations, the series includes 4 forward gears...
line.
Turbo-Hydramatic 125
The 3-speed Turbo-Hydramatic 125 was introduced in 1980 and produced through 2002. It carried over some parts from the light-duty Turbo-Hydramatic 200 and 350, but was generally a new design.The 125 was renamed 3T40 later, following GM's new naming convention. The 4T40-E
GM 4T40 transmission
The 4T40-E and 4T45-E are a series of automatic transaxles from General Motors. Designed for transverse engine configurations, the series includes 4 forward gears...
replaced it starting in 1995.
Applications:
- 1982–1996 A-bodyGM A platform (FWD)The General Motors A platform was a mid-size car automobile platform designation used from 1982 to 1996. Previously the A body designation had been used for rear wheel drive mid-sized cars....
- 1980–1985 X-bodyGM X platformThere have been two X-body automobile platforms from General Motors. All X-bodies were small entry-level models.-Rear wheel drive:The rear-wheel drive X-body underpinned the Chevrolet Nova and similar cars of the late 1960s and 1970s. It was also the basis for the Cadillac Seville's K platform...
- 1982–2002 J-bodyGM J platformThe J platform, or J-body, was General Motors' inexpensive front-wheel drive automobile platform from the 1980s and 1990s. The platform replaced the GM H platform. The J-platform is the only platform of GM to have a model in each of its "Original 5" passenger car divisions...
- 1990-1993 W-bodyGM W platformThe W-body is an automobile platform from General Motors which underpins mid-size cars with front-wheel drive. The platform, originally code named GM10, began in 1982 under Chairman Roger B. Smith and debuted in 1988 with the Pontiac Grand Prix, the Buick Regal, and the Oldsmobile Cutlass Supreme...
- 1987–1996 L bodyGM L platformThe General Motors L platform was a front-wheel drive compact car automotive platform that was produced from 1987 through 1996....
- 1990–1995 U-body vansGM U platformThe U-platform is a front wheel drive minivan and crossover SUV platform from General Motors produced since 1990. North American sales ended in 2009, but Chinese production continues. The minivans were divided into three generations, 1990-1996, 1997-2005 and 2005-current...
(with LG6 engine) - 1984-1988 Pontiac FieroPontiac FieroThe Pontiac Fiero is a mid-engined sports car that was built by the Pontiac division of General Motors from 1984 to 1988. The Fiero—meaning "proud" in Italian and "wild", "fierce", or "ferocious" in Spanish—was designed by George Milidrag and Hulki Aldikacti as a Pontiac sports car...
Turbo-Hydramatic 125 C
This was a later model of the 125 that debuted for 1982, and included an ECUEngine Control Unit
An engine control unit is a type of electronic control unit that determines the amount of fuel, ignition timing and other parameters an internal combustion engine needs to keep running...
controlled solenoid
Solenoid
A solenoid is a coil wound into a tightly packed helix. In physics, the term solenoid refers to a long, thin loop of wire, often wrapped around a metallic core, which produces a magnetic field when an electric current is passed through it. Solenoids are important because they can create...
that would engage 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...
into "lock up" where engine power was transferred directly to the transaxle. The C comes from the use of a torque converter clutch (TCC). The solenoid that controls this is notorious for failure, their failure is indicated by an engine stall when braking from speeds greater than 55 MPH. This occurs because the clutch does not disengage and the engine cannot produce enough output to keep the vehicle in motion.
Turbo-Hydramatic 440-T4
A breakdown of THM440T4 is: Turbo HydraMatic Model 440 - Transversely Mounted - 4 Speed Fully Automatic transmissionA 4-speed version of the 125 was created for the 1985–1986 GM C platform (FWD)/GM H platform (FWD)
GM H platform (FWD)
The H platform, or H-body designates a General Motors front wheel drive full-sized automobile platform beginning in 1986. It is related to the C, G and K platforms.Previously the H platform designation was used for unrelated rear-wheel drive compact cars....
cars, the Turbo-Hydramatic 440-T4. Many parts were identical to the 125, though it was generally stronger and included an 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...
fourth gear. This transmission was first used in GM's 1985 Buick Park Avenue, Oldsmobile 98, and Cadillac Deville. In 1986, after switching to FWD, the Buick LeSabre, Oldsmobile Delta 88, and later, the Pontiac Bonneville also used this transmission. A special strengthened F-7 version was also used for the 1987–1992 Cadillac Allanté
Cadillac Allanté
The Allanté was Cadillac's first venture into the ultra-luxury roadster market. The vehicle was sold from 1987 until 1993, with roughly 21,000 models built over its 7-year production run...
.
One unique feature of this transmission is its use of both a modulator valve and a throttle valve (TV) cable. Most transmissions either use one or the other to control shift points and shift smoothness. On the Turbo 440-T4, the TV cable exclusively controls the shift points, while the modulator valve controls the shift feel. This feature makes it very easy for a home, "shadetree" mechanic to adjust the transmission shift points with minimum effect on the shift feel.
The 440-T4 was originally slated to be used with downsized C body cars for 1984, however, issues with failures led to introduction being delayed until 1984 for the 1985 model year.
The 440-T4 was later renamed the 4T60.
A heavy-duty version of the 4T60 was used for the 1989-1990 Pontiac Turbo Grand Prix.
The electronically-controlled 4T60-E was introduced in 1991. It would become the basis of the GM 4T65 transmission, still used today.
A heavy-duty version of the 4T60-E was used only in 1996 L67 Equipped vehicles.
Applications:
- 4T60
- 1988-1994 W platform
- 1985-1993 H/C platform
- 1985-1993 A platform
- 1988-1990 Buick Riviera/Reatta
- 1985-1990 Cadillac models
- 4T60-HD
- 1989-1990 Turbo Grand Prix
- 4T60-E
- 1997-1999 Buick Century
- 1994-1996 A platform
- 1991-1999 W platform (some models)
- 1991-1993 Cadillac models
- 1991-1997 H/C platform
- 1990-1992 Oldsmobile Toronado
- 1990-1993 Buick Reatta
- 1990-1993 and 1996 Buick Riviera
- 1994-1996 Corsica/Beretta
- 1992-1996 U platform (with L27 and LA1 engines)
- 4T60-E HD (When Equipped with L67 Engine)
- 1996 Buick Park Avenue
- 1996 Oldsmobile 88
- 1996 Pontiac Bonneville
- 1996 Buick Riviera
- F-7
- 1987–1992 Cadillac AllantéCadillac AllantéThe Allanté was Cadillac's first venture into the ultra-luxury roadster market. The vehicle was sold from 1987 until 1993, with roughly 21,000 models built over its 7-year production run...
- 1987–1992 Cadillac Allanté