That's right, Lonnie. The Hydramatic (not sure about the dash) originated in 1938, and it had a clutch. By 1940 or so, they had developed a fluid coupling so the engine could idle at a stop. Some WW II tanks used Cadillac engines and Hydramatic transmissions. The Hydramatic was used in non-GM cars like Nash after the war, as well as Olds, Pontiac, and Cadillac cars. Buick had the Dynaflow, and Chevy had the Powerglide, starting in 1951. GMC trucks used the Hydramatic with either a Pontiac V-8, or an inline 6-cylinder during the early 50's. I can remember driving a GMC road tractor, pulling a dozer on a lowboy, in the early 60's with a Hydramatic in it. The most recent overhaul I've done on one of those transmissions was from an early-60's Pontiac Grand Prix with a controlled-coupling Hydro. That's the aluminum-case trans you're thinking about, the 1956 to 63 Controlled Coupling. There are a couple of "O" rings, 1/16" square, and about 9" in diameter on the controlled coupling torus which are the pits to assemble without cutting them! Pontiac and Olds used a "Roto-Hydramatic" in the mid-60's somewhere that was a real POS!
Jerry
