Editing Automatic transmission (section)

====1939–1964: Early hydraulic automatics====
The General Motors [[Hydra-Matic]] became the first mass-produced automatic transmission following its introduction in 1939 (1940 model year). Available as an option in cars such as the [[Oldsmobile Series 60#1939–1940|Oldsmobile Series 60]] and [[Cadillac Sixty Special#1938–1941|Cadillac Sixty Special]], the Hydra-Matic combined a [[fluid coupling]] with three [[hydraulics|hydraulically controlled]] planetary gearsets to produce four forward speeds plus reverse. The transmission was sensitive to engine throttle position and road speed, producing fully automatic up- and down-shifting that varied according to operating conditions. Features of the Hydra-Matic included a wide spread of ratios (allowing both good acceleration in first gear and cruising at low engine speed in top gear) and the fluid coupling handling only a portion of the engine's torque in the top two gears (increasing fuel economy in those gears, similar to a [[Lock-up clutch|lock-up]] torque converter). Use of the Hydra-Matic spread to other General Motors brands and then to other manufacturers starting 1948 including [[Hudson Motor Car Company|Hudson]], [[Lincoln Motor Company|Lincoln]], [[Kaiser Motors|Kaiser]], [[Nash Motors|Nash]], [[Holden]] (Australia), as well as [[Rolls-Royce Motor Cars|Rolls-Royce]] and [[Bentley]] licensing production in the UK and providing the transmission to [[Jensen Motors]], [[Armstrong Siddeley]] and other UK manufacturers.<ref>{{cite web | url=https://ateupwithmotor.com/terms-technology-definitions/rolls-royce-automatic-gearbox | title=Don't Call It Hydra-Matic: The Rolls-Royce and Bentley Automatic Gearbox < Ate up with Motor | date=4 September 2022 }}</ref> During World War II, the Hydra-Matic was used in some military vehicles.

The first automatic transmission to use a torque converter (instead of a fluid coupling) was the Buick [[Dynaflow]], which was introduced for the 1948 model year. In normal driving, the Dynaflow used only the top gear, relying on the torque multiplication of the torque convertor at lower speeds. The Dynaflow was followed by the Packard [[Ultramatic]] in mid-1949 and the Chevrolet [[Powerglide]] for the 1950 model year. Each of these transmissions had only two forward speeds, relying on the converter for additional torque multiplication. In the early 1950s, [[BorgWarner]] developed a series of three-speed torque converter automatics for car manufacturers such as American Motors, Ford and Studebaker. [[Chrysler]] was late in developing its own true automatic, introducing the two-speed torque converter [[PowerFlite]] in 1953, and the three-speed [[TorqueFlite]] in 1956. The latter was the first to utilize the Simpson compound planetary gearset.

In 1956, the General Motors Hydra-Matic (which still used a fluid coupling) was redesigned based around the use of two fluid couplings to provide smoother shifts. This transmission was called the ''Controlled Coupling Hydra-Matic'', or "Jetaway" transmission. The original Hydra-Matic remained in production until the mid-1960s at GM, with the licensed Rolls-Royce Automatic transmission soldiering on until 1978 on the [[Rolls-Royce Phantom VI]]. In 1964, General Motors released a new transmission, the [[Turbo Hydramatic]], a three-speed transmission which used a torque convertor. The Turbo Hydramatic was among the first to have the basic gear selections (''park'', ''reverse'', ''neutral'', ''drive'', ''low'') which became the standard gear selection used for several decades.