The main automatic transmission to employ a torque converter (in lieu of a fluid coupling) was the Buick Dynaflow, which was launched for the 1948 product year. In usual driving, the Dynaflow used just the top rated gear, counting on the torque multiplication in the torque convertor at decrease speeds. https://elliottvcdca.blogpostie.com/55617221/5-simple-statements-about-gearbox-auto-explained