Ford C4 & C6 Automatic Transmissions

C4 & C6 Transmission Gear Ratios

Ford C4 Transmission Specs

The C4 is a medium duty, 3 speed automatic transmission manufactured from 1964 to 1981. It was available in the 1973 to 1977 Ford Bronco and 1965 to 1981 Ford F-series. It is praised for its simplicity and durable, though it is a step down from the heavy duty C6. To save weight, the C4 was manufactured with an aluminum case. The transmission can be separated into three sections - the bell housing, the transmission case or center section, and the tail housing. Like the C6, the C4 relied on a Simpson planetary gearset.

The C4 did evolve over the course of its life, meaning earlier versions are not necessarily identical to later versions. From 64 to 69, the C4 was built with a 0.788 inch, 24 spline input shaft. In 1970, this was upgraded to a 26 spline, 0.839 inch shaft, and in 1971 the input shaft was revised yet again so that it was 26 splines on the torque converter side and 24 splines at the clutch hub. Like the C6, there is tremendous aftermarket support for the C4 and the transmissions can be built to survive significantly more torque than originally intended.

Ford C6 Transmission Specs

The C6 is arguably one of the most popular automatic transmissions Ford ever produced. Built from 1966 to 1996, the C6 was manufactured at Ford's Livonia Transmission Plant in Livonia, Michigan until the mid 1980s when production was moved to the Sharonville Transmission Plant in Ohio. The C6 is praised for its strength, reliability, and simplicity. It remains a popular choice in a number of motorsports, including drag racing and off-road vehicles. The heavy duty C6 features a Simpson planetary gearset and Borg Warner flexible shift band. The C6 is a 1 piece casting with the bellhousing integrated into the case. Three tailshaft housing lengths were available: 17.4 inches for Lincoln cars, 7 inches for Ford trucks, and 14 inches for Ford passenger cars.

When it was introduced in 1966, it was built to be a heavy duty, light weight, less complex transmission than its predecessors. By today's standards, the transmission has a high level of parasitic loss due to its component weight and size. The C6 transmission platform was used as the foundation of another popular Ford transmission, the E4OD. The 3 speed C6 was offered in the Ford F-Series from 1967 to 1996 and the Ford Bronco from 1978 to 1991. 5 bell housings were used:

• Cleveland bell housing for the 351M, 400, and all Ford 385 family engines.
• Windsor bell housing for the 300 "Big Six" I-6, all Windsor engines, and the 351 Cleveland.
• FE bell housing pattern specifically for the Ford FE family engines.
• Diesel bell housing, similar to the FE and 385 but with no interchangeable parts.
• Mel 462, a rare bell housing pattern used in the 1966 to 1968 462 V-8 Lincoln Continental and 1968 to 1970 460 V-8 Lincoln Continental.