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 more simple replacement for the original Ford-O-Matic two speed transmission being used in smaller, less powerful cars.
Because of its cast iron construction, the Ford-O-Matic was very heavy. In designing the C4, Ford used an aluminum alloy, three-piece case (bell housing, main case, and tailhousing). The aluminum case and the use of a more simple Simpson planetary gearset reduced the weight significantly. It was primarily used with Ford's inline six-cylinder engines and small V8 engines (see Ford Windsor engines), usually up to 302 in³ (5.0 L). 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. Some C4s were built with a larger spread bell housing to use with 351M V8s, but these are rare.