The initial automatic transmission to use a torque converter (rather than a fluid coupling) was the Buick Dynaflow, which was released for that 1948 model calendar year. In usual driving, the Dynaflow employed only the top rated gear, depending on the torque multiplication on the torque convertor at reduce speeds. https://gearboxauto75285.jts-blog.com/33120187/5-simple-techniques-for-gearbox-auto