The very first automatic transmission to work with a torque converter (instead of a fluid coupling) was the Buick Dynaflow, which was introduced with the 1948 product year. In typical driving, the Dynaflow employed just the major gear, depending on the torque multiplication on the torque convertor at decreased speeds. https://gearboxauto19741.tusblogos.com/34037441/new-step-by-step-map-for-gearbox-auto