Corvair Powerglide
Encyclopedia
Chevrolet Corvair Powerglide is a two-speed automatic transmission
designed specially for the then all-new 1960 Chevrolet Corvair
compact car that emerged in the fall of 1959 as Chevrolet's competitor in the then booming small car market. The Corvair was powered by a six-cylinder rear engine that necessitated a specially designed transaxle. Corvair Powerglide took the principles of the standard Chevrolet
Powerglide
and modified them to suit the rear mounted powertrain location of the new Corvair. The Corvair used the Powerglide for all 10 years it was produced; from 1961 to 1963, Pontiac
used a modified version of Corvair Powerglide it called 'TempesTorque' for its front-engine, rear-transaxle Tempest
, LeMans
and Tempest LeMans
cars.
mounted remotely on the rear face of the differential, (that also incorporates the starter ring gear, and a centrifugal fan baffle for cooling, via slots in the engine bellhousing) and is driven directly from the engine crankshaft by a flexplate inside the engine bellhousing. The selector quadrant is arranged R-N-D-L, or Reverse, Neutral, Drive and Low, with no "Park" (except in Pontiac's 1963 version, redesigned to handle the increased torque of a new V8 engine in Tempest and LeMans, added by means of a separate lever). Range selection is via dash-mounted selector lever operating a sheathed cable that moves a spool valve range selector in the transmission valve body.
Due to the rear-mounted engine, the differential lies between the transmission and engine
, so drive to the transmission from the engine is carried forward via a hollow turbine shaft from the engine mounted torque converter
to the transmission gearbox. Power from the gearbox was carried rearward again to the differential pinion gear via yet another, concentric hollow shaft of larger diameter. A small concentric shaft inside the turbine shaft operated the front pump of the transmission to permit engagement of drive/reverse ranges when the car was stopped or moving slowly; at speeds over 15 mph (24.1 km/h), a differential-driven (from the car motion) rear pump of smaller capacity and greater efficiency took over and the front pump shut down to improve fuel economy.
The Corvair Powerglide provided one reduction range and reverse, in addition to direct drive and neutral. Low and Reverse ranges were a 1.82 ratio reduction, using a single planetary gearset. Locking the planetary geartrain provided a 1:1 direct drive. The differential driven rear pump permitted push-starting the Powerglide-equipped Corvair, at speeds over 18 mph (29 km/h) by creating adequate pressure to engage low band and turn over the engine via the torque converter. A multiple disc clutch engaged reverse range, low was braked using a band on the forward clutch drum, and direct provided via clutches. The torque converter
of the Corvair offered 2.6:1 reduction at stall
, and improved car performance when engine speeds were below ~2000 rpm.
When starting out in Drive range, low gear was automatically selected and the low band applied under pressure modulated by a vacuum modulator which sensed engine output and adjusted clutch and band apply pressures to provide smooth engagement without slip. As the vehicle accelerated, rear pump output would increase and initiate a shift to direct. The rear pump pressures were modified by a throttle valve, and governor
, both of which could delay the upshift, or even trigger a forced downshift at driver command. Full throttle downshifts were achieved by the throttle valve which permitted the transmission to stay in low range or be forced into downshifting to speeds between 45–50 mph (72.4–80.5 km/h). At speeds under 35 mph (56.3 km/h), heavy throttle would delay upshifts, or initiate a forced 'detent touch' kickdown for better performance. When Low Range or Reverse are selected, the apply pressures are not modulated and the full line pressure of the transmission
is applied to ensure positive engagement. The multiple plate reverse clutch and double wrap low band design offered a slight buffer to engagement to prevent harshness even under high apply pressures. A quite sophisticated valve body timed shifts and apply pressures carefully in Drive range to ensure smoothness and prevent 'hunting' between gears, which is a common complaint of small cars with automatic transmission. Corvair Powerglides had a good reputation for reliability and were ordered on a large majority of Corvair passenger cars.
Corvair Powerglide was an all-new design, but borrowed a couple small parts from Chevrolet Turboglide
and its operating concept is very similar to conventional Chevy Powerglide. Aluminum Powerglide, introduced in the conventional Chevrolet models in 1962 (starting with Chevy II) incorporated many features pioneered by Corvair Powerglide, scaled up slightly for the larger passenger car and light truck lines. The Corvair was originally intended to be only available with Powerglide, but late in its development, a manual transmission was also designed to help lower the base sticker price for its 1960 introduction. The Corvair Powerglide transmission remained largely in its original design throughout the Corvair's production, which ended in May 1969.
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...
designed specially for the then all-new 1960 Chevrolet Corvair
Chevrolet Corvair
-First generation :The 1960 Corvair 500 and 700 series four-door sedans were conceived as economy cars offering few amenities in order to keep the price competitive, with the 500 selling for under $2,000...
compact car that emerged in the fall of 1959 as Chevrolet's competitor in the then booming small car market. The Corvair was powered by a six-cylinder rear engine that necessitated a specially designed transaxle. Corvair Powerglide took the principles of the standard Chevrolet
Chevrolet
Chevrolet , also known as Chevy , is a brand of vehicle produced by General Motors Company . Founded by Louis Chevrolet and ousted GM founder William C. Durant on November 3, 1911, General Motors acquired Chevrolet in 1918...
Powerglide
Powerglide
The Powerglide is a two-speed automatic transmission designed by General Motors. It was available primarily on Chevrolet from January, 1950 through 1973, although some Pontiac models also used this automatic transmission, extensively on models produced for the Canadian market with Chevrolet...
and modified them to suit the rear mounted powertrain location of the new Corvair. The Corvair used the Powerglide for all 10 years it was produced; from 1961 to 1963, Pontiac
Pontiac
Pontiac was an automobile brand that was established in 1926 as a companion make for General Motors' Oakland. Quickly overtaking its parent in popularity, it supplanted the Oakland brand entirely by 1933 and, for most of its life, became a companion make for Chevrolet. Pontiac was sold in the...
used a modified version of Corvair Powerglide it called 'TempesTorque' for its front-engine, rear-transaxle Tempest
Pontiac Tempest
The Pontiac Tempest was an entry-level compact produced by the Pontiac Motor Division of General Motors, introduced in September 1960 for the 1961 model year....
, LeMans
Pontiac LeMans
The Pontiac LeMans was a model name applied to compact and intermediate-sized automobiles offered by the Pontiac division of General Motors from 1962 to 1981. The LeMans was replaced by the downsized Pontiac Bonneville for the 1982 model year...
and Tempest LeMans
Pontiac Tempest
The Pontiac Tempest was an entry-level compact produced by the Pontiac Motor Division of General Motors, introduced in September 1960 for the 1961 model year....
cars.
Operation
Corvair Powerglide is a fully automatic, two-speed, aluminum-cased automatic transmission mounted directly to the forward face of the cast iron differential housing. It uses a three-element, welded assembly 10 in (25.4 cm) diameter torque converterTorque 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...
mounted remotely on the rear face of the differential, (that also incorporates the starter ring gear, and a centrifugal fan baffle for cooling, via slots in the engine bellhousing) and is driven directly from the engine crankshaft by a flexplate inside the engine bellhousing. The selector quadrant is arranged R-N-D-L, or Reverse, Neutral, Drive and Low, with no "Park" (except in Pontiac's 1963 version, redesigned to handle the increased torque of a new V8 engine in Tempest and LeMans, added by means of a separate lever). Range selection is via dash-mounted selector lever operating a sheathed cable that moves a spool valve range selector in the transmission valve body.
Due to the rear-mounted engine, the differential lies between the transmission and engine
Engine
An engine or motor is a machine designed to convert energy into useful mechanical motion. Heat engines, including internal combustion engines and external combustion engines burn a fuel to create heat which is then used to create motion...
, so drive to the transmission from the engine is carried forward via a hollow turbine shaft from the engine mounted 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...
to the transmission gearbox. Power from the gearbox was carried rearward again to the differential pinion gear via yet another, concentric hollow shaft of larger diameter. A small concentric shaft inside the turbine shaft operated the front pump of the transmission to permit engagement of drive/reverse ranges when the car was stopped or moving slowly; at speeds over 15 mph (24.1 km/h), a differential-driven (from the car motion) rear pump of smaller capacity and greater efficiency took over and the front pump shut down to improve fuel economy.
The Corvair Powerglide provided one reduction range and reverse, in addition to direct drive and neutral. Low and Reverse ranges were a 1.82 ratio reduction, using a single planetary gearset. Locking the planetary geartrain provided a 1:1 direct drive. The differential driven rear pump permitted push-starting the Powerglide-equipped Corvair, at speeds over 18 mph (29 km/h) by creating adequate pressure to engage low band and turn over the engine via the torque converter. A multiple disc clutch engaged reverse range, low was braked using a band on the forward clutch drum, and direct provided via clutches. 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...
of the Corvair offered 2.6:1 reduction at stall
Stall (engine)
A stall is the slowing or stopping of a process, and in the case of an engine, refers to a sudden stopping of the engine turning, usually brought about accidentally....
, and improved car performance when engine speeds were below ~2000 rpm.
When starting out in Drive range, low gear was automatically selected and the low band applied under pressure modulated by a vacuum modulator which sensed engine output and adjusted clutch and band apply pressures to provide smooth engagement without slip. As the vehicle accelerated, rear pump output would increase and initiate a shift to direct. The rear pump pressures were modified by a throttle valve, and governor
Governor
A governor is a governing official, usually the executive of a non-sovereign level of government, ranking under the head of state...
, both of which could delay the upshift, or even trigger a forced downshift at driver command. Full throttle downshifts were achieved by the throttle valve which permitted the transmission to stay in low range or be forced into downshifting to speeds between 45–50 mph (72.4–80.5 km/h). At speeds under 35 mph (56.3 km/h), heavy throttle would delay upshifts, or initiate a forced 'detent touch' kickdown for better performance. When Low Range or Reverse are selected, the apply pressures are not modulated and the full line pressure of the 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...
is applied to ensure positive engagement. The multiple plate reverse clutch and double wrap low band design offered a slight buffer to engagement to prevent harshness even under high apply pressures. A quite sophisticated valve body timed shifts and apply pressures carefully in Drive range to ensure smoothness and prevent 'hunting' between gears, which is a common complaint of small cars with automatic transmission. Corvair Powerglides had a good reputation for reliability and were ordered on a large majority of Corvair passenger cars.
Corvair Powerglide was an all-new design, but borrowed a couple small parts from Chevrolet Turboglide
Turboglide
The Turboglide is a Chevrolet constant torque automatic transmission that made its debut as an optional transmission on Chevrolet V8 passenger cars for 1957. It consisted of a concurrently geared planetary gearbox with a 'switch pitch' dual pitch torque converter stator...
and its operating concept is very similar to conventional Chevy Powerglide. Aluminum Powerglide, introduced in the conventional Chevrolet models in 1962 (starting with Chevy II) incorporated many features pioneered by Corvair Powerglide, scaled up slightly for the larger passenger car and light truck lines. The Corvair was originally intended to be only available with Powerglide, but late in its development, a manual transmission was also designed to help lower the base sticker price for its 1960 introduction. The Corvair Powerglide transmission remained largely in its original design throughout the Corvair's production, which ended in May 1969.