Ford C4 transmission
| C4/C5 | |
|---|---|
| Overview | |
| Manufacturer | Ford Motor Company |
| Production | 1964–1986 |
| Body and chassis | |
| Class | 3-speed longitudinal automatic transmission |
| Related | Ford C6 |
| Chronology | |
| Predecessor | Ford-O-Matic |
| Successor | AOD |
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.
Ford used the term "SelectShift" because placing the gear selector in second gear forced the transmission to start and remain in second gear only, regardless of engine revolutions, or torque being sent to the unit. If the transmission was placed in third gear, the transmission would start in first gear, then shift to second and third gear as normal.
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. A few were also used with FE engines, mostly the 390. in full-size cars. Ratios are 2.46 low, 1.46 second and direct high.
The early model C4 (1964–1969) used a .788-inch 24-spline input shaft, which was upgraded in 1970 to 26-spline and .839-inch. The upgrade also included a matching clutch hub of 26-spline. In 1971, Ford went to a 26/24-spline input shaft, meaning the torque-converter side is 26-spline and the clutch hub is 24-spline.
The C4 was also found with valve bodies requiring a different number of bolts, 8-bolt vs 9-bolt. A 9-bolt valvebody can be used on either case, but a nut & bolt must be used on the valve body in the empty hole, dropping the bolt in from the top and using the nut on the bottom/filter side.
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