All Hydra-Matics in 1954 (actually late 40's thru 1964) were 4 speeds
forward. Top gear is 1.00 (NOT overdrive) ratio. I believe '54 was the
first year that Chevy pickups were available with Hydra-Matics. GMC
trucks started using them in '52. Original Hydra-Matic was in '39
Oldsmobile. Caddy offered it in '40 and Pontiac followed in '48. World
War II M-5 Light Tanks, M-8 Howitzers and M-24 Light Tanks used a pair
of Caddy flathead V8 with Hydra-Matics. In '56 the "dual range"
Hydra-Matic was replaced with the "controlled coupling" Hydra-Matic in
all except trucks and Rolls Royce/Bentley. RR continued to use dual
range Hydra-Matics until they adopted the TH-400 in 1967 (after 2 years
of letting GM work out any bugs). Other automakers that bought
Hydra-Matics from GM included Hudson, Willys, Lincoln, Kaiser and Nash.
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