The primary automatic transmission to utilize a torque converter (as opposed to a fluid coupling) was the Buick Dynaflow, which was introduced for that 1948 design calendar year. In normal driving, the Dynaflow employed just the major gear, depending on the torque multiplication from the torque convertor at reduce speeds. https://gearbox-auto63950.blogpostie.com/55617222/gearbox-auto-for-dummies