The 1st automatic transmission to implement a torque converter (as an alternative to a fluid coupling) was the Buick Dynaflow, which was introduced with the 1948 design year. In ordinary driving, the Dynaflow applied only the leading gear, counting on the torque multiplication on the torque convertor at lower speeds. https://traviseebzx.blogdiloz.com/32684923/getting-my-gearbox-auto-to-work