The first automatic transmission to use a torque converter (instead of a fluid coupling) was the Buick Dynaflow, which was released for that 1948 design year. In ordinary driving, the Dynaflow made use of just the best gear, depending on the torque multiplication with the torque convertor at decreased speeds. https://devinelmpo.blog5star.com/34634206/gearbox-auto-can-be-fun-for-anyone