Bronco C-4 Parts Beef-up:
To me the C-4 is by far the easiest and least expensive to rebuild, or repair. However, If you have hard part damage it can get expensive. This is why you immediately stop driving your C-4 equipped vehicle when there are metal shavings in the pan or the gearbox is making noise while driving. The following are some ideas that have helped me produce some of the strongest, and longest lasting C-4 I have ever seen.
1) Install a “C” Type intermediate servo assembly in it. If a “C” is not available, the “H” type will do fine.
2) A hardened input shaft and Forward drum assembly will be needed if you are using a high horsepower engine to its limits. The stock truck input shaft will be fine for stock, mildly, and moderately built performance engines.
3) A B&M Transpack Valve body Kit Or TransGo Shift Kit® installed on the heavy duty setting.
4) A good auxillary trans cooler (Tru-Cool brand) This alone is the best thing you can do for even a stock C-4 to help it live a long time.
5) a C-6 pump bushing pressed in flush with the gear cavity. This bushing is wider than the C-4 bushing and will support the converter hub with more surface area
6) A solid intermediate band (not the flex type) should be used with the “C” servo. The Borg Warner Flex band will do just fine and will work beautifully with the “H” servo.
7) All new bushings throughout.
8) PA performance 6-Pinion front planetary gear set.
9) Use new thrust washers where needed and adjust the end-play to .008”-.012”
Friction materials:
Borg Warner Clutches are my favorite for Street and Heavy duty use.
If you are racing it, Alto Reds or Raybestos Reds are a good choice
If the rest of the hard parts are tight (planetaries, pump, low roller clutch), it will easily handle more horse power than your Dana 20 will.
Where to buy parts:
I buy most all my parts through my local Axoiom Distribution Center because they know me and give me the best price breaks. Transtar and Natpro are also excellent resources for top quality parts.
http://www.atcdg.com , or
http://www.transtarindustries.com/
http://www.natpronet.com/index.htm
Or your local Transmission Repair shop. They will have most of what you need on hand or they will order for you what they don't.
The high performance hard parts such as the input shaft and front planetary, I buy from Summit.
As for the "C" Type Servo, They are very rare, I found mine in the boneyard on a 68 Econoline but I've seen them on 66 shelby mustangs too. A company called Sonnax has Billett reproductions of the C-type that all the above mentioned parts sources can get for you.
If you don't want to go through the trouble and expense, the H-type servo is the next best thing, and is found on C-4 equipped trucks. The 73-77 Broncos it should have been factory equipment. If you still need one, the H-servo can also be found on 67-73 mustangs cougars with 4-barrell small blocks (302-289) and 2-barrell Cleveland motors in 72 torinos, montegos, and rancheros.
More about the intermediate servos:
The Intermediate servo is that round thing up front on the right side. It's cast aluminum and is held in place by 4 bolts with 1/2" wrench size. There is usually an ID tag bolted to one of the two lower bolts. On the cover of the servo the letter "H" should be cast right into it and be visible from underneath the truck.
What this servo does is apply the Intermediate Band (second gear band)(Front Band) The "C" servo has the most surface area I have ever seen on any factory C-4, thus it will apply the band with more pressure and you will get a more positive, stronger band apply in 2nd gear. Under a heavy engine load or high horsepower situation, it will be least likely to slip and burn up the lining on your band. Instead it will probably bark the tires on the 2nd gear shift