There were at least 3 versions of the Hydramatic. The original one came out in Olds and a very few Buicks 1938 or 39, with a manual clutch. In 1940 Oldsmobile added a fluid coupling (not a torque converter) that allowed the engine to idle in gear. GMC used the transmission in military 6X6 trucks during WW II, and it was used behind Cadillac flathead V8 engines (2 of them) in a light tank.
After the war, Cadillac, Olds, Pontiac, Nash and GMC truck used the transmission in its second generation model which did not have the Dual Range capability. In 1954, Dual Range added a selector position to lock the transmission in 3rd. gear up to about 65 MPH depending on rear end ratio, and them made a forced shift to prevent engine damage. In 1956-57 the Controlled Coupling Hydramatic was introduced in cars, not trucks. It was sometimes called the "Jetaway" which was actually incorrect. The Controlled Coupling Hydramatic continued until 1964 in Olds, Pontiac and Cadillac, along with a really crappy version called the "Roto Hydramatic" (AKA "Slim Jim"). In 1965 the 3-speed Turbo 350 replaced all the previous models, and the Turbo 400 was the heavy duty option, also a direct drive 3 speed.
Chevy and GMC continued to use the original Dual range transmission in trucks long after cars went to the Controlled Coupling and Roto models. I believe 1962 was the last year of production, as they were not used behind the 230/250/292 engines.
Jerry
