<P> The original Hydra - Matic incorporated two features which are widely emulated in today's transmissions . The Hydra - Matic's ratio spread through the four gears produced excellent "step - off" and acceleration in first, good spacing of intermediate gears, and the effect of an overdrive in fourth, by virtue of the low numerical rear axle ratio used in the vehicles of the time . In addition, in third and fourth gear, the fluid coupling only handled a portion of the engine's torque, resulting in a high degree of efficiency . In this respect, the transmission's behavior was similar to modern units incorporating a lock - up torque converter . </P> <P> In 1956, GM introduced the "Jetaway" Hydra - Matic, which was different in design than the older model . Addressing the issue of shift quality, which was an ongoing problem with the original Hydra - Matic, the new transmission utilized two fluid couplings, the primary one that linked the transmission to the engine, and a secondary one that replaced the clutch assembly that controlled the forward gearset in the original . The result was much smoother shifting, especially from first to second gear, but with a loss in efficiency and an increase in complexity . Another innovation for this new style Hydra - Matic was the appearance of a Park position on the selector . The original Hydra - Matic, which continued in production until the mid-1960s, still used the reverse position for parking pawl engagement . </P> <P> The first torque converter automatic, Buick's Dynaflow, was introduced for the 1948 model year . It was followed by Packard's Ultramatic in mid-1949 and Chevrolet's 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 American Motors, Ford Motor Company, Studebaker, and several other manufacturers in the US and other countries . 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 . </P> <P> General Motors produced multiple - turbine torque converters from 1954 to 1961 . These included the Twin - Turbine Dynaflow and the triple - turbine Turboglide transmissions . The shifting took place in the torque converter, rather than through pressure valves and changes in planetary gear connections . Each turbine was connected to the drive shaft through a different gear train . These phased from one ratio to another according to demand, rather than shifting . The Turboglide actually had two speed ratios in reverse, with one of the turbines rotating backwards . </P>

Who is the auto of the article transmitted transmission