The initial automatic transmission to use a torque converter (rather than a fluid coupling) was the Buick Dynaflow, which was released to the 1948 model year. In regular driving, the Dynaflow made use of just the prime gear, counting on the torque multiplication from the torque convertor at decreased speeds. https://gearboxauto50369.blog4youth.com/34413844/5-easy-facts-about-gearbox-auto-described