The Ford C4 is a three-speed, light-duty automatic transmission introduced in the 1964 model year and produced through 1981
It featured an aluminum alloy 3 piece case (bellhousing, main case, and tailhousing). This was significantly lighter than earlier cast iron Cruise-O-Matic designs. It also used a Simpson planetary gearset.
It was used with Ford's inline six-cylinder engines and small V8 engines (see Ford Windsor engines), usually up to 302 cubic inches/5.0 liters. By comparison, the 351 Windsor and 351 Cleveland small- and intermediate-block engines were backed by the medium-duty FMX. A few C4s were built with a big-block bellhousing to use with Ford 335 engines, notably the 351M, but these are very rare.
It is especially notable as the original automatic transmission option in the Ford Mustang.
Modified C4s remain popular with hotrodders and drag racers due to their simplicity and durability.
The C-4 in my car sucks most of the torque and half the horsepower out of the engine before it ever gets to the wheels.