C4 rebuild advice

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ESHALLBETTER
Posts: 1564
Joined: Fri Dec 11, 2009 8:49 am
Bronco Info: 85 class 3, 70's somthing trail bronco.
Location: Minneapolis, MN

C4 rebuild advice

Post by ESHALLBETTER »

Hey Guys,

I have a C4 in my 72 and it's puking fluid out the bellhousing anytime the truck is in gear. This leads me to believe the pump seal is going out in the trans. I have too much going on right now, so this one is going to have to visit the tranny shop I am thinking...

That said, since it has to come out, I am looking for recommendations on fixing any weak links in the thing. I don't want to break the bank, it's just one of those "well, since it's coming out anyway I may as well fix the ______ or add a _______" type situations. The truck has a stock FI Explorer motor, and is locked both ends on 35's (I will mount my 40's once I get bigger axles), and has a Winters gate shifter. I use it mostly for trail riding.

Any advise on what to do to the thing when the tranny comes out is appreciated.

Thanks!
300
Posts: 647
Joined: Tue Jan 26, 2010 4:44 pm
Bronco Info: 1979 Class 3 Race Bronco. Built in 2000.

Re: C4 rebuild advice

Post by 300 »

I have used C4's for many years in street vehicles, just could never make one survive in a racer. In the circle track car, we ran it in first gear with the engine going to 6500 rpm twice each lap, can't imagine why it was so unhappy!!! Finally was able to get it through a season by pulling it and going through it every two weekends. Looking back, it is likely the reason it was having so many problems was because I had nowhere near enough cooling.

Suggestions for your application if you want to go further than a stock rebuild:
- Put a temperature guage in the pan and if it gets hot, figure out why and fix it.
- Regardless of what the advertisement says on the cooler, use a bigger one or more of them to keep the thing cool.
- The cooler circuit feeds the entire rear section of the trans with lube and cooling, and this is where the planetaries are. You MUST keep them cool to keep them alive, assuming you are not running in high gear all the time.
- The drums and hubs internally can be drilled to promote more fluid flow through the friction disks and planetaries
- Replace the thrust washers with needle roller bearings. TCI makes a kit for C6's, not sure if there is one for the C4, but it really helps the C6.
- There were some companies that were working on planetaries with additional gears, but I don't know if any of them have them available. The failures I saw I believe were more related to heat than load.
- Drill and tap some tiny screws in the front pump cover to retain the front seal. Had one pop out once loading the car on the trailer on the way to a race that afternoon.
- There are higher performance versions of most friction disks available from just about any supplier. I have used both and can't really say I could notice the difference, but the cost is only a few bucks more.
- Make sure the bushings are in good shape and not egged out. If the one in the front pump (torque converter support) is worn, the front seal will give you trouble. There are a ton of bushings internally in there. Replacements are surprisingly cheap but changing them all takes a lot of labor and/or special tools. With the exception of the front and rear bushings (2wd tailhousing), I have not seen the internal ones wear much.
- Not sure if you are using a full manual valve body, but if you do, it eliminates a ton of parts and mechanisms in there. I used a B&M manual/automatic kit on the first one I ever rebuilt and proceeded to drive it 150K miles in a Mustang and loved the way it worked. B&M is not the same company it was back then.
- With a manual valve body, you can set the line pressure to 195 psi, and that should get you through anything.

You could likely just change the front seal and go on if there were no other problems.
pieron22
Posts: 14
Joined: Tue May 08, 2012 2:32 pm
Bronco Info: Autofab C&T crossover steering 16"king co's&bumps 9"35spl 4link
Location: Shickshinny PA

Re: C4 rebuild advice

Post by pieron22 »

I agree with 300 on cooling!! I run a c4 behind a 347, 33" tires, 4.56 gears, and a converter i believe about 500 over stock or so. We race back here in PA @ LM4W.org. Tight woods racing, not too hi-speed like out west. I had failures when we first started, but figured them out. keep a low stall converter in it. We used #6 lines to rear mounted cooler, again like 300 said, use cooler with as many passes in it as physically possible, and make sure the pressure line to cooler (the 1 closest to bellhousing) is plumbed into the BOTTOM of cooler so as to push fluid thru cooler then return line out TOP back to rear most fitting on trans. Found this out accidentally by reversing the lines during pre-race cleaning and over heatin trans. Used fittings on trans so AN lines used 90 deg ends for more flow than a 90 deg pipe fitting. Little things added up for more cooling on our rig. Have Artcarr Reverse Man valve body with compression braking, I like it, BUT it's not a jake brake!! Inside case on return port (again rear most port) we drilled out passage to bearings because I think only like 1/8" hole stock. Definately? replace planetery with aftermarket ones ( think we used TCI, plus they sell hardened shafts for C4). On the pump, my trans builder driller out that checkball and plugged passage, this gives pull pressure to cooling circuit. After 1st race we smoked front seal , called Artcarr and their comment "EVERYONE knows to drill/plug checkball on pump for a C4". This is after their directions for valvebody says "bolt-in installation". Silly me 4 not doing homework. This all worked for me, BUT there is some maintenance needed with the C4, I use Broncograveyard's deep trans pan, adds 2 quarts & I think delrae 16 passage cooler. They aren't as strong as C6, but lighter for smaller motors like mine. This is only my opinions on what works for us & hope to learn more from the guys here
Broncodawg
Posts: 711
Joined: Fri Dec 11, 2009 10:14 pm
Bronco Info: Ole Yeller- 89 Bronco prerunner, 77 Bronco rock rig, 79 F100 prerunner barn find
Location: Bishop, CA

Re: C4 rebuild advice

Post by Broncodawg »

Wow, learned more about the c4 in the last two posts than I could ever hope for. Large cooler on mine is doing the job, but one day this info will be going with me to the tranny shop. Thanks for taking the time to learn us up on c4s.
Prizefighter
Posts: 48
Joined: Tue Aug 28, 2012 5:32 pm
Bronco Info: 1978 Ford Bronco, 74 Bronco
Location: Texarkana, AR

Re: C4 rebuild advice

Post by Prizefighter »

This is great information, will be using this soon. Will be running a 347/c4 in stock class.
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