The initial automatic transmission to utilize a torque converter (as opposed to a fluid coupling) was the Buick Dynaflow, which was released for the 1948 product calendar year. In normal driving, the Dynaflow used only the leading gear, depending on the torque multiplication on the torque convertor at reduced speeds. https://gearbox-auto19630.blog-kids.com/34001054/indicators-on-gearbox-auto-you-should-know