The very first automatic transmission to implement a torque converter (rather than a fluid coupling) was the Buick Dynaflow, which was launched for the 1948 model 12 months. In ordinary driving, the Dynaflow used only the top gear, depending on the torque multiplication of the torque convertor at lower speeds. https://collintusro.snack-blog.com/33616087/not-known-facts-about-gearbox-auto