The first automatic transmission to make use of a torque converter (rather than a fluid coupling) was the Buick Dynaflow, which was released for the 1948 design year. In ordinary driving, the Dynaflow used just the top gear, depending on the torque multiplication in the torque convertor at decrease speeds. https://gearbox-auto63186.slypage.com/34224274/gearbox-auto-things-to-know-before-you-buy