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Ford Bronco Parts - Classic Vintage Early Bronco Parts

C4 Valve body service and modifications

Tech article by BwoncoHowie and filed under - Automatic

Tech article by BwoncoHowie

The purpose of this article is to explain and cover some basic info about do it yourself C-4 Valve body service. The actual valve body is from a 1974 Bronco, therefore the illustrations may differ slightly from what you may be working on.  If you are inexperienced as a mechanic, perhaps you should get help when performing the steps shown below. It is recommended that you read the entire article first so you may prepare all the tools and materials as well as a clean work environment. After reading through the article first, you can then make notes on where your valve body may need attention. Some steps that are performed later may be mentioned early in the article in order to save time and computer space. VB is referring to Valve Body.

VB disassembly starts with the removal of these 2 bolts shown circled in green below.

Note: The 2 dots show where the Kick-down lever and the pin on the rooster comb must go to be properly indexed while installing the VB back into the Trans.

C4-valve-body-01

Next, remove the long main filter bolts and the 9 shorter VB bolts. Notice the correct location of the ID tag. This picture shows the throttle pressure limit valve and spring have not yet been removed. You should remove them at this time before taking the VB halves apart.

C4-valve-body-02

When the VB halves were first split apart the hockey puck was stuck to the separator plate indicated by the arrow. The circles show the proper locations of the viton shuttle ball and puck. Discarding the puck from the assembly will aid in firming up the shifts and will not hurt the transmission.

C4-valve-body-03

Next, remove the bolt holding the separator plate and gasket to the channel plate. Note proper locations of the 2 remaining Viton Check Balls. The one in the bathtub is mandatory; the other one can be removed for a firmer 3rd gear shift. The channel plate is where a lot of sediment can collect and it is very important to clean it thoroughly. After cleaning with a suitable solvent, these components should be dried with compressed air in order to keep foreign particles like dirt and rag lint to a minimum. We refer to these channels that the hydraulic pressure travels through as “Worm Tracks”.

C4-valve-body

Drill separator in 2 locations as shown. Remember, these modifications are non reversible unless you have a spare unmodified separator plate. If you are unsure about having a firm shift, you can use the next two smaller drill bits 7/64” and 3/32” accordingly for a less aggressive modification that is near stock but slightly firmer. Caution: Do not drill any holes larger than 1/8” This is unnecessary and can cause valve body cross leakage and gasket damage.  Drilling these holes larger than 1/8” is also rough on the rest of the Bronco drivetrain, Axles, U-Joints, Splines, Differentials, Transfer Cases, and Motor Mounts, etc. A high speed steel counter sink bit works very well for taking burrs off of holes that have been enlarged. (See last photo # 23)

C4-valve-body

This picture shows a 2 oz. ball peen hammer and a 3/8” steel ball bearing being used to knock down the sharp edges around the 2 holes on the separator plate where the shuttle balls need to travel. By doing this you will add longer life to the Viton Checkball. Do this to the plate in each of the 2 bathtub locations on the side of the plate that actually makes contact with the shuttle ball (Viton Checkball). Also prepare the 3rd check ball location, it’s the larger hole that covers the single well used by the direct clutch feed passage. You don’t need to tap it very hard because all you are doing is dulling the sharp edge left by the factory hole punch and making a tapered seat for the ball to seal against.  I’m using a machined flat piece of steel as a backing plate during this modification.

C4-valve-body

The next picture shows the valve components from left to right and top to bottom in that order. After cleaning, all valves must move freely in their perspective bores.

1. Shift valve retaining plate.

2. 1-2 Shift valve.

3. Manual 2nd valve.

4. 1-2 Shift valve spring.

5. 2-3 Shift valve.

6. 2-3 Shift valve spring.

7. Throttle Modulator Valve.

8. Retaining plate for Transition and Cutback valves.

9. Transition valve spring, (outlined in red) which should be removed and discarded for Heavy Duty use

10. Transition valve.

11. 2-3 Back-out valve.

12. 2-3 Back-out valve spring

13. Cut-back valve, which uses no spring. For Heavy Duty and street versions, this valve can be blocked by inserting a spare viton checkball in the bore before inserting the valve and retaining plate, noted by the red dot.

C4-valve-body

This picture shows the shift valves installed after cleaning. They have been lubricated with a 50/50 mixture of Slick50 and Type-F transmission fluid. Note the spring tension is pushing the valves partially out of their bores. Install all valves and their retaining plates but when tightening the retaining plate bolts make sure the retaining plate will have plenty of clearance with the separator plate when the valve body halves are bolted together.

C4-valve-body

This picture shows the proper order of the servo accumulator valve.

C4-valve-body

By reversing the order of the spring to the outboard area of the valve will cause a firmer 2nd gear shift. You may not want to perform this modification at first. Experimenting with the other milder mods first, may give you the desired results.

C4-valve-body

The main pressure regulator valve, and the Booster valve with its sleeve is shown removed for cleaning purposes. Note the spring retainer slips over the tail of the valve. And the smaller Booster spring rests inside the larger pressure regulator spring. Use a dab of Vaseline to hold the booster valve in its sleeve for easier assembly of the pressure regulator valve and springs. Vaseline has a low melting point and is perfectly compatible with all transmission fluids. The booster sleeve is retained by a small spring-clip, some models will use an (L)-pin in this location.

Pressure regulator components are shown from left to right in this order.

1. Retainer clip and booster valve sleeve.

2. Booster valve

3. Main pressure regulator spring.

4. Booster valve spring

5. Spring retainer

6. Main pressure regulator valve.

C4-valve-body

Check the operation of the kick-down valve by pushing the plunger shown in the first picture, make sure it moves freely and returns fully after the valve casting half has been cleaned with solvent and dried with compressed air. You may also move the other remaining valves with a pick/scribe to assure that they slide freely in their bores. If any of these valves are sticking or frozen, It is recommended that they be removed from their bores and the valve casting be cleaned carefully.

The picture shows a pick being used to move the valves against spring tension to see if they return to the home position.

C4-valve-body

After cleaning and assembling the valves, and cleaning and removing all traces of dirt and old gasket material, you will be ready to assemble the VB halves together. Start by selecting the proper gasket and with a few drops of trans oil, position the new gasket on the plate. Make sure the gasket is on the correct side between the separator plate and the lower VB channel plate. Position the gasket so all the holes are centered as much as possible. Some commercial Valve body modification service packages may ask you to delete this gasket. If your VB shows signs of having commercial aftermarket VB modifications installed, it may already have this gasket missing. If so, do not re-install a new gasket.

C4-valve-body

The next step is to turn the plate over and make sure no holes are blocked by a mis-aligned or wrong gasket.

C4-valve-body

The plate can then be placed over the channel plate. Make sure the necessary shuttle ball is in place and if desired, replace the 3rd gear Kick-down check ball.

Here again shows the channel plate and check balls before the separator plate is placed into position.

C4-valve-body

Secure the separator plate with gasket to the channel plate with 1 of the short 10-24 bolts finger tight to make up the channel plate sub-assembly and set aside.

This picture shows the valve casting assembled, with the check ball and hockey puck already installed; ready for attachment to the channel plate and separator plate sub-assembly.  Refer back to illustration No. 3 to see the proper location of the hockey puck and shuttle ball.

C4-valve-body

This picture shows the channel plate assembly with the valve body in position. Note the 2 quarter 20 bolts installed only finger tight at this point. A pair of tapered awls used in 2 specific locations for aligning the separator plate with the channel plate. At the time these awls were purchased I thought that MAC TOOLS made the best tools for this particular job. Tapered punches or dowels can also be used for this.  These are the only 2 holes that should be used to align the plates before tightening the bolts.

  • 120 inch pounds on the ¼-20 bolts.
  • 46 inch pounds on the 10-24 bolts.

C4-valve-body

The following picture shows a well proven tightening sequence for these particular fasteners. The last bolt shown by the arrow, is installed loosely for alignment purposes during the assembly of the valve body. It will be removed and re-installed again after the valve body has been bolted-up to the transmission case. If you use a torque wrench, and have the ability to work in a clean environment, you are well on your way to putting together a quality piece of craftsmanship.

C4-valve-body

You should always try to include a filter gasket when doing work on the Bronco C-4 filter, even a used metal gasket is better than none at all. Be sure to install the throttle pressure limit valve and spring before installing the filter screen. NOTE; The Bronco specific sump pick-up pipe is missing from the filter in this illustration. It will be installed into the filter before the transmission pan is installed.

C4-valve-body

This picture shows the 2-3 shift valve and spring, and the throttle pressure limit valve and spring for size comparison. Notice the shift valve spring is slightly longer. The springs are very similar, don’t get them mixed-up.

C4-valve-body

This picture shows the filter being positioned, again using a tapered awl for alignment of the filter, and filter gasket with the bolt hole before tightening the filter bolts. Refer back to the tightening sequence to complete the filter installation. Don’t forget the 3 bolts on the other side need tightening, and it doesn’t hurt to double check the valve retaining plate bolts, if you leave them loose, you will get no upshift. With all the bolts properly torqued, this VB is ready for installation.

C4-valve-body

A little something regarding screens and filters:

With the C-4, always use them whenever possible, they will save you a lot of time and headaches. Ford engineers put them there for a good reason, clean and re-use them don’t leave them out!  The C-5 uses the same screens and they are no longer available new. So if you need them try to get them from a used transmission where the last technician had enough sense to put them back where they belong.

On the left is the Governor screen, it is installed in the governor support distributor housing feed passage before installing the governor valve assembly. Service to the governor will not be included in this tech article, but I thought it was important enough to mention the need for this screen that is commonly deleted from the assembly during service. On the right is pictured the larger pump pressure port screen, which is installed in the case passage before the valve body is installed. There are 2 ports that are often confused that this screen will fit in. Correct installation is in the port closer to the shift lever.  Both of these screens can help to save you from having sticky valves and damage due to particle contamination in the valve housings.

C4-valve-body

Here is a picture of my countersink drill bit I use it in the drill chuck with very light pressure to remove rough edges after drilling/enlarging holes in the separator plate.

C4-valve-body

I hope you enjoy reviewing this info as much as I enjoyed sharing it with you.

I also wish you success with your VB repairs and hope this article is helpful for those of you who want to improve the performance of your C-4 or just make the VB function correctly.

Tech article by BwoncoHowie

3 Responses to “C4 Valve body service and modifications”

  1. bigun-1 Says:

    Great Artical!!

    I have been building transmission’s for over 20yr’s.
    One thing that I might add is DON’T tighten the valve retaining plate bolt’s until the valve body halve’s have been torqued. It is difficult and in some case’s a socket must be ground down to accomplish the tighting, but it will save you possible headache’s down the line.

  2. BwoncoHowie Says:

    I agree Bigun. Thanks for the idea and the kind words. I suppose with as many of these as i have done, I could probably do it blindfolded. I guess Im so used to checking the clearance of the valve retaining plates before tightening them and I dont have a special thin-wall socket, that I forgot to mention it.

  3. wheelsblank27 Says:

    I just rebuilt my 70’s case fill c4 with all the input ive gotten on this post and help from members. I used the transgo valve body shif kit and enlarged the 2 holes 1 below a 1/8″ for firm but not chirping tires and a bigger inter. Servo. Also included in my purchase of my c4 were c5 clutch packs a v8 valve body ( it came out of a v6 car) and new front pump. So I built a Frankenstein tranny and am about to install next week. I had to also get a used adapter shaft and retainer. Balding it was easy. And fun!

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