The first fully automatic transmission used in a production car, GM’s Hydra-Matic, was introduced in 1939.
Oldsmobile began production of the Hydra-Matic in 1939 for the 1940 model year. Unlike earlier semi-automatic systems, it did not require the driver to operate a clutch pedal during normal driving. It combined a fluid coupling with hydraulically controlled planetary gearsets, allowing the car to start and shift through four forward speeds automatically.
The date can cause confusion because automotive history often gives both the introduction year and the model year. The transmission entered production and Oldsmobile cars were shipped in 1939, while those vehicles were marketed as 1940 models. Earlier experiments and semi-automatic transmissions existed, but they did not meet the same definition of a fully automatic, mass-produced passenger-car transmission.
Hydra-Matic’s success led to wider adoption within General Motors and licensing or supply arrangements with other manufacturers. Later automatics increasingly used torque converters, but the original Hydra-Matic used a fluid coupling.