The Ford C4 is a three-speed, medium-duty automatic transmission introduced on 1964 model year vehicles and produced through 1981.
The C4 was designed to be a lighter and simpler replacement for the original Ford-O-Matic two speed transmission being used in smaller, less powerful cars.
The aluminum case and the use of a simpler Simpson planetary gearset reduced the weight significantly (estimated at 185 lbs (83.9Kg)).
By comparison, the 351 Windsor and 351 Cleveland small and intermediate-block engines were backed by the medium-duty FMX or the heavy-duty C6 that debuted in 1966.
Modified C4s remain popular with hot rodders and drag racers due to their simplicity and durability.