The first automatic transmission to make use of a torque converter (rather than a fluid coupling) was the Buick Dynaflow, which was released for that 1948 design year. In usual driving, the Dynaflow utilised only the major gear, relying on the torque multiplication with the torque convertor at reduced speeds. https://gearbox-auto18517.blog-ezine.com/34283266/gearbox-auto-secrets