While there is much variation within each type, in a very general sense there are two types ofmotor vehicletransmissions:
Manual – The driver performs each gear change by operating a gear shift lever combined with a manually operated clutch.
Automatic – Once the driver place a gear range selector in its automatic position, usually "Drive" or "D," the transmission selects gear ratios based on many factors, including engine speed, vehicle speed, engine load, accelerator position, gear range selector position, road incline/decline, and more.
For the purposes of this article, there are two primary types ofengine orientation:
Longitudinal – These transmissions are designed to work with engines that are mounted in the vehiclelongitudinally, meaning that the engine's crankshaft is oriented in the same direction as the length of the car, front to back. The transmission is often designed separately from the final drive components, including the rear axle differential. In rare cases (such as the 1961-63Pontiac Tempest, as well as rear-engined cars such as the originalVolkswagen Beetle and theChevrolet Corvair) the transmission and rear axle are combined into a single unit called atransaxle.
Transverse – These transmissions are designed to work with engines that are mountedtransversely in a front-wheel drive vehicle, meaning that the engine's crankshaft is oriented in the same direction as the width of the car, left to right. These vehicle applications combine the transmission and front axle intotransaxles. Many such vehicles orient the engine/transmission combination so that the transmission is on the left side of the vehicle and the engine is on the right, although exceptions may exist. Often the transmission and the final drive portions are combined into a single housing because of restricted space.
Several types of automatic and manual transmissions are described below, all of which may be found in both longitudinal and in transverse orientations, depending on engineering need, cost, and manufacturer choice.
The General MotorsAutomatic Safety Transmission (AST) was asemi-automatic transmission released in 1937. The first mass-produced fully-automatic transmission developed for passenger automobile use was the GMHydra-Matic introduced in the autumn of 1939 as a (very likely subsidized) $57 option for the 1940Oldsmobile.[1] The Hydra-Matic was then offered byCadillac starting with its 1941 models, and byPontiac for 1948. It enjoyed wide success. Also for 1948,Buick introduced itsDynaflow automatic transmission, and for 1950,Chevrolet offered thePowerglide automatic. This meant that, by 1950, GM marques offered three automatic transmissions at a time when most of its competitors still offered none.
Throughout the 1950s, allGM Marques continued developing automatic transmission designs, both jointly and independently. Early models included:
1937–1939 GMAutomatic Safety Transmission (AST) — Offered byOldsmobile for 1938-1939, and byBuick in 1938 only. This was a semi-automatic transmission that required the driver to use a clutch to get the car moving, but once underway, the AST shifted itself. The clutch was only needed if the driver needed to use the gear selector lever, for example, to shift into reverse.
1940–1967 GMHydra-Matic — The first automotive automatic transmission, a 4-speed unit, introduced for 1940 byOldsmobile, and ultimately also offered byPontiac andCadillac. Except for its name, it bore no relation to the later GMTurbo Hydramatic, 3-speed automatic transmission that was introduced in 1964.
1947–1952 BuickDynaflow — The firstBuick automatic transmission, a 2-speed unit, introduced for 1948. It was designed for smoothness and shifted without any perceptible gear changes, somewhat similar to modern continuously-variable transmissions. For this reason, vintage car enthusiasts today sometimes call it "Buick's 2-speedCVT."
1950–1973 ChevroletPowerglide — The firstChevrolet automatic transmission, a 2-speed unit, introduced for 1950 and offered on both passenger cars as well as Chevrolet and GMC trucks. The Powerglide automatic transmission was also offered at different times byPontiac,Holden,Vauxhall andOpel passenger cars.
1953-1955 BuickTwin-Turbine Dynaflow — For 1953, Buick introduced the 2-speed Twin-Turbine Dynaflow, a redesigned Dynaflow automatic transmission employing two turbines and a single stator for improved responsiveness and efficiency.
1956-1957 BuickTwin-Turbine 2 Dynaflow — For 1956, Buick offered the 2-speed Twin-Turbine 2 Dynaflow, a second redesign of the Dynaflow automatic transmission. The Twin-Turbine Dynaflow included turbines and a variable-pitch stator that changed pitch angle based on accelerator position for better responsiveness.
1956-1964 GMDual-Coupling/Controlled-Coupling Hydra-Matic — For 1956, GM offered the first substantial redesign of the 4-speed Hydra-Matic automatic transmission. Along with numerous technical improvements, this new Hydra-Matic automatic transmission also included a Park position, something previous Hydra-Matic units did not offer (drivers locked the transmission by shifting into Reverse and turning the ignition switch off). This new Hydra-Matic was also called the Cadillac 315/P315 Hydra-Matic, the Oldsmobile Jetaway/StratoFlight, and the Pontiac Super Hydra-Matic.
1957-1961 ChevroletTurboglide — For 1957,Chevrolet offered a new kind of automatic transmission that employed a constant-torque design that offered imperceptible shifts. The 3-speed Turboglide was not popular, as buyers thought it felt odd. It had poor reliability until a 1959 redesign (which helped, but came too late). The Turboglide was only offered on V8 models. TheCorvette only offered the Powerglide automatic at this time.
1958-1959 BuickFlight Pitch Dynaflow/Triple Turbine — This was the third redesign of the Buick Dynaflow automatic transmission, a 3-speed automatic transmission that featured three turbines. It bore more than a passing resemblance to the Chevrolet Turboglide, even though Chevrolet and Buick worked separately on their transmission designs. It was called the "Flight Pitch Dynaflow" in 1958, and for 1959 it became the "Triple Turbine," as Buick moved away from the "Dynaflow" name. Beset with many teething pains, this transmission was only offered for 1958 and 1959.
1961-1963 BuickDual-Path Turbine Drive. This 2-speed automatic transmission was used by Buick after it discontinued the Triple Turbine automatic.
1962-1972 PontiacTempestTorque — This was a 2-speed automatic transmission that was based on the Chevrolet Powerglide.
1964-1969 GMSuper Turbine 300 — This 2-speed automatic transmission was a lower cost unit that was used on someBuick models as the "ST-300," someOldsmobile models as the "Jetaway," and somePontiac cars as simply the "Automatic."
1968-1971 ChevroletTorque-Drive — Offered for a few years byChevrolet, this was a two-speed semi-automatic transmission based on the Powerglide. There was no clutch, but drivers had to use the column-mounted shift lever to shift between low and high gears. Only available with 6-cylinder engines, the Torque-Drive didn't cost much less than the Powerglide, and did not sell well.
Introduced in 1964, the GMTurbo-Hydramatic was an entirely new 3-speed automatic that featured a torque converter, as opposed to the standard fluid coupling that the original Hydra-Matic used. Buick, Cadillac, Oldsmobile, and Pontiac began offering the Turbo-Hydramatic fairly quickly after its introduction. By contrast, Chevrolet took much longer to replace the aging two speed Powerglide with the three speed Turbo-Hydramatic in its lineup, at first not offering the Turbo-Hydramatic at all, then only offering it on the most costly and powerful V8 engines on full size models, then finally offering it with all engines on full- and midsized models ... but not in the compact Nova. It finally took until 1973 before Chevrolet finally phased out the by then badly outdated Powerglide automatic transmission, long after the other GM divisions discontinued their old automatic units.
Across the GM divisions, the Turbo-Hydramatic was called simply the "Hydramatic," with a few exceptions, such as Buick's use of the term "Super Turbine 400." In Argentina, the Turbo Hydra-Matic was marketed as the "Chevromatic" in the 1970s. Starting in the early 1980s, the Turbo-Hydramatic was gradually supplanted by four-speed automatics, some of which continued to use the "Hydramatic" trade name.
Initially, models were designated with the letters TH/THM/ST followed by the series/version number. In 1987, GM switched to a simpler naming scheme for their transmissions (Example: 4L80E)
The next-generation transmissions, introduced in the early 1990s, were the electronicHydra-Matics, still based on theTurbo-Hydramatic design. Most early electronic transmissions use the "-E" designator to differentiate them from their non-electronic cousins, but this has been dropped on transmissions with no mechanical version like the newGM 6L transmission.
Borg-Warner T-50 transmission — 5-speed longitudinal manual transmission. (Used by GM in its RWDH-body cars and a few other limited light duty applications from 1976 to 1978.)
Getrag 260 — 5-speed longitudinal manual transmission made byGetrag.
Muncie M20 — 4-speed longitudinal wide-ratio manual transmission (AKA Muncie 4-speed) made by GM at their Muncie, Indiana factory, 1963-1975.
Muncie M21 — 4-speed longitudinal close-ratio manual transmission made by GM at their Muncie, Indiana factory.
Muncie M22 — 4-speed longitudinal heavy duty close-ratio manual transmission (AKA 'Rock Crusher') made by GM at their Muncie, Indiana factory.
Muncie M62/M64 — 3-speed longitudinal transmission made by GM.
Muncie SM318 transmission — 3-speed transmission transmission used from 1954 through 1969 in both passenger car and truck applications. Also found in wide- and narrow-ratio configurations.
Muncie SM420 transmission — 4-speed manual transmission used up to 1967. Very similar to the Muncie SM465 except for small changes to its gear ratios and the location of its reverse gear.
Muncie SM465 — 4-speed longitudinal manual transmission used in 1968-1991 Chevrolet 1/2-ton, 3/4-ton, and 1-ton trucks.
New Process Gear A833 (RPO MY6 or MM7) — 4-speed longitudinal overdrive transmission made by New Process Gear for early- to mid-1980s General Motors light trucks.
New Process Gear NP435 — 4-speed longitudinal transmission used in a limited number of 1967-1972 GM pickup trucks.
Saginaw M15 — 3-speed longitudinal light duty (less than 300 horsepower) manual transmission (AKA Saginaw 3-Speed) made by GM at their Saginaw, Michigan factory.
Saginaw M26/27 — 4-speed longitudinal light duty (less than 300 horsepower) wide-ratio manual transmission made by GM at their Saginaw, Michigan factory.
Tremec T-5 — 5-speed longitudinal manual transmission currently made byTremec. Originally made byBorg-Warner.
^Hendrickson, James; Holmes, Alan G.; Freiman, David (2009).General Motors Front Wheel Drive Two-Mode Hybrid Transmission. SAE World Congress & Exhibition.doi:10.4271/2009-01-0508.
^Miller, Michael A.; Holmes, Alan G.; Conlon, Brendan M.; Savagian, Peter J. (2011). "The GM 'Voltec' 4ET50 Multi-Mode Electric Transaxle".SAE International Journal of Engines.4 (1):1102–1114.doi:10.4271/2011-01-0887.
^Conlon, Brendan M.; Blohm, Trevor; Harpster, Michael; Holmes, Alan G.; Palardy, Margaret; Tarnowsky, Steven; Zhou, Leon (2015). "The Next Generation 'Voltec' Extended Range EV Propulsion System".SAE International Journal of Alternative Powertrains.4 (2):248–259.doi:10.4271/2015-01-1152.
