The main automatic transmission to make use of a torque converter (in place of a fluid coupling) was the Buick Dynaflow, which was introduced for the 1948 model year. In ordinary driving, the Dynaflow used just the top rated gear, depending on the torque multiplication with the torque convertor at https://gearboxauto09641.newsbloger.com/34413478/a-simple-key-for-gearbox-auto-unveiled