Ford C4 transmissions
Rebuild and re-assemble of a Ford C-4 transmission
Basic rebuild information
- This article is a work in progress.
- This WIKI is not intended to be a replacement for an ATSG tech manual. First time builders will likely need a tech manual.
- This is not a step-by step pictorial, don't assume it is shown where every part goes.
Main case prep work
Notice the fresh bushing installed in the case. Good idea to replace the bushing. While the bushing is out, check the oil return hole from the cooler system for size and restrictions. Often builders drill the oil return hole about 30% larger than the OEM hole. A 0.200" or 0.210" drill bit size works well.
Parking pawl wheel and thrust washer
Thrust washer for parking pawl wheel shown in photo.
Parking pawl wheel with thrust washer installed. Washer held in place with assembly grease.
Here the governor support is seen with oil transfer tubes installed.
Main case roller clutch, rear band, and drum install
This view shows the rear band installed with the apply struts set in place
This view shows the rear roller clutch and race installed. The rollers have accordion style springs that push the rollers towards the race. You set the race in place first. Set the rollers in place next, and install the springs last. Watch the spring install as sometimes they like to turn sideways at one end.
Snap ring installed on the output shaft. Snap ring sets on top of the rear ring gear before the rear planet is installed. This retains the shaft into the transmission. If the snap ring will not go into the groove, recheck the parts installation to resolve the clearance problem.
Thrust washer installed on rear planetary unit, a little assembly grease can hold it in place.
Assemble drums, thrust washers, and planetary gear
Photo below shows front planetary with matching ring gear. Ring gear has fresh bushing installed.
Photo of typical C4 modulator valve, pin and vacuum modulator. Factory length on modulator pin is 1.620", that may vary 0.010" or 0.015". A longer pin (0.030" - 0.045") will firm up shifts and the shift will be slightly later. A shorter pin does the opposite.
Some modulators are "thread in" design (early trans, pre- 1970). Push in design shown in photo. The pin must be there for proper operation of the modulator.
Rollerized gear train
Rollerizing replaces the thrust washers with torrington bearings to reduce drag on the gear train. This process requires a quality lathe and tooling to cut the needed grooves. A set of calipers for measuring depth and thickness is also needed.
Rear band drum with bearing installed into a machined groove. You must take into account the bearing thickness over the thrust washer that is replaced. This difference is the depth of the groove for the bearing to set in.
Rear ring gear hub with bearing installed. Ring gear not seen in this photo.
Rear planetary unit with bearing sitting out of groove for illustration.