The primary automatic transmission to employ a torque converter (in place of a fluid coupling) was the Buick Dynaflow, which was launched for that 1948 design calendar year. In usual driving, the Dynaflow employed just the top gear, depending on the torque multiplication with the torque convertor at decrease speeds. https://gearboxauto41739.blazingblog.com/34161244/5-simple-statements-about-gearbox-auto-explained