The very first automatic transmission to employ a torque converter (in lieu of a fluid coupling) was the Buick Dynaflow, which was launched for that 1948 product year. In usual driving, the Dynaflow applied only the major gear, relying on the torque multiplication of your torque convertor at lower speeds. https://keegangjgfc.blogdigy.com/5-essential-elements-for-gearbox-auto-51124518