Hydramatic is an automatic transmission developed by both General Motors' Cadillac and Oldsmobile divisions. Introduced in 1939 for the 1940 model year vehicles, the Hydramatic was the first mass-produced fully-automatic transmission developed for passenger automobile use.
A Hydra-Matic Drive transmission, produced between 1939 and 1956, on display at the Ypsilanti Automotive Heritage Museum
A Hydra-Matic 315 transmission, produced between 1956 and 1964
A Hydra-Matic 240 transmission, produced between 1961 and 1964
A Hydra-Matic 375 transmission, produced between 1961 and 1964
An automatic transmission is a multi-speed transmission used in motor vehicles that does not require any input from the driver to change forward gears under normal driving conditions. Vehicles with internal combustion engines, unlike electric vehicles, require the engine to operate in a narrow range of rates of rotation, requiring a gearbox, operated manually or automatically, to drive the wheels over a wide range of speeds.
Cutaway view of a 2007 Toyota AA80E hydraulic automatic
Typical gear selector for an automatic transmission
Cutaway view of a ZF 8HP transmission: torque converter on the left, planetary gearsets in the centre, control mechanisms at the bottom
Torque converter – cutaway view
