The main automatic transmission to make use of a torque converter (as opposed to a fluid coupling) was the Buick Dynaflow, which was released for your 1948 product 12 months. In typical driving, the Dynaflow used only the top rated gear, relying on the torque multiplication in the torque convertor https://daltonwdghh.bloggip.com/34215278/gearbox-auto-for-dummies