The main automatic transmission to use a torque converter (as opposed to a fluid coupling) was the Buick Dynaflow, which was launched for that 1948 product calendar year. In normal driving, the Dynaflow utilized just the best gear, counting on the torque multiplication with the torque convertor at lower speeds. https://angelomuxyy.blogdigy.com/the-greatest-guide-to-gearbox-auto-51123923