The first automatic transmission to work with a torque converter (as opposed to a fluid coupling) was the Buick Dynaflow, which was launched for that 1948 model year. In ordinary driving, the Dynaflow utilized only the major equipment, counting on the torque multiplication in the torque convertor at lower speeds. https://gearbox-auto65308.blogdomago.com/32712879/gearbox-auto-fundamentals-explained