C4 Issue

C4 Issue

Joined: June 24th, 2012, 5:26 pm

June 26th, 2012, 2:16 pm #1

I have a C4 with a reverse manual transbrakre valve body. The issue I am having is the transbrake will not hold the truck(jumps forward), and third gear is slipping. We did a line pressure test on it and the results were as follows(all readings taken Park 200 psi
Reverse 140-150
Neutral 200 psi
1st 200 psi
2nd 200 psi
3rd 150 psi

In reverse if you bring the rpm up to about 2-2500 the pressure shoots to 400-450 psi, all other gears go no higher than 225 psi. Also with the transbrake engaged the pressure shoots up to 400-450 psi.

Any ideas on what the issue is?
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Joined: July 17th, 2011, 7:07 pm

June 26th, 2012, 3:59 pm #2

3rd clutch is probably burnt.
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Joined: June 24th, 2012, 5:26 pm

June 26th, 2012, 8:24 pm #3

Sorry, I forgot to mention this is a fresh tranny. All new clutches,steels, and seals. It has maybe 2 miles of street driving and 3 1/8th mile passes. Found out at the track there was an issue and have not moved it since.
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Joined: July 17th, 2011, 7:07 pm

June 26th, 2012, 9:16 pm #4


You say it slips in 3rd.... so the problem is likely in the 3rd clutch somewhere...

Could be internal pressure leak to 3rd.

It doesn't take much to scorch a set of clutches.

If 3rd pressure is leaking the clutch would burn on one pass.
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Joined: January 1st, 2004, 2:15 am

June 27th, 2012, 12:58 am #5

Sorry, I forgot to mention this is a fresh tranny. All new clutches,steels, and seals. It has maybe 2 miles of street driving and 3 1/8th mile passes. Found out at the track there was an issue and have not moved it since.
Pop the pan and valve body and run an air test. It'll quickly tell you if you have a problem with the seals. And hopefully you ran an air test prior to putting it together?
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tom
tom

June 28th, 2012, 1:30 am #6

The pressures told you the problem. Problem is the direct clutch/cluthes/seals/rings any or all the above. Pullit back out. Check to make sure that the valve body is supposed to have that much line pressure. 200 is ok but 400? I don't think so.
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Joined: June 24th, 2012, 5:26 pm

June 28th, 2012, 5:56 am #7

Thanks for the info. I just got it pulled out tonight(which sucks have to pull the engine and tranny together), I will get to check it out in a day or two.
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