The first automatic transmission to utilize a torque converter (as an alternative to a fluid coupling) was the Buick Dynaflow, which was launched to the 1948 design yr. In normal driving, the Dynaflow utilized just the prime gear, depending on the torque multiplication on the torque convertor at decreased speeds. https://kylertxvvq.jts-blog.com/33119851/new-step-by-step-map-for-gearbox-auto