The very first automatic transmission to use a torque converter (in place of a fluid coupling) was the Buick Dynaflow, which was released to the 1948 design yr. In usual driving, the Dynaflow used only the best gear, counting on the torque multiplication in the torque convertor at reduce speeds. https://tysoncmopp.dailyhitblog.com/39563944/the-basic-principles-of-gearbox-auto