The very first automatic transmission to implement a torque converter (as an alternative to a fluid coupling) was the Buick Dynaflow, which was introduced for that 1948 product year. In ordinary driving, the Dynaflow used just the top rated gear, counting on the torque multiplication from the torque convertor at https://stephenxhlor.blogspothub.com/33247337/5-simple-statements-about-gearbox-auto-explained