The Hydra-Matic was the first mass-produced fully auto transmission available starting with Olds in 1939, then Cadillacs in the next year, and used into the 60s. GM has a history of excellent automatic transmissions. In fact, this four speed transmission was original equipment in the 50s in Lincolns (1949 to 1954), Nashes, Ramblers, Kaisers, Willys and Hudsons.  Rolls Royce built it for themselves and Bentley from 1952 through 1967.