The primary automatic transmission to use a torque converter (as opposed to a fluid coupling) was the Buick Dynaflow, which was introduced to the 1948 design 12 months. In ordinary driving, the Dynaflow used only the prime equipment, relying on the torque multiplication on the torque convertor at lower speeds. https://gearbox-auto08528.wizzardsblog.com/34090220/a-review-of-gearbox-auto