John,
The Hydra-Matic transmission was "battle tested" during WWII - "perfected" might have been a word used by some GM PR people?
Military service brought no dramatic design changes to the Hydra-Matic transmission, but it forced GM to resolve many of its early teething problems. After the war, Cadillac and Oldsmobile advertising would, with some justice, proclaim that Hydra-Matic was “battle tested.”"The H-M transmission was used on M2-M5 "light" tanks, and the M24 "light" tanks.
