The first automatic transmission to use a torque converter (as an alternative to a fluid coupling) was the Buick Dynaflow, which was launched for that 1948 model yr. In usual driving, the Dynaflow employed just the best gear, counting on the torque multiplication with the torque convertor at reduced speeds. https://gearboxauto97529.spintheblog.com/34183735/indicators-on-gearbox-auto-you-should-know