The initial automatic transmission to use a torque converter (as opposed to a fluid coupling) was the Buick Dynaflow, which was launched for that 1948 model 12 months. In normal driving, the Dynaflow used just the leading gear, counting on the torque multiplication on the torque convertor at decreased speeds. https://gearbox-auto07283.ageeksblog.com/33026098/considerations-to-know-about-gearbox-auto