98 Chevy 4L60E Burnt Forward Clutches ARB

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tschafers
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98 Chevy 4L60E Burnt Forward Clutches ARB

Post by tschafers » Fri Jan 24, 2014 6:09 pm

I rebuilt this trans 6 weeks ago and it worked great for 5 weeks then it started slipping in forward gears. I put a pressure gauge on it and did not see anything I was too alarmed at so I pulled the pan and found clutch dust. I then removed the filter cut it open and found a piece of a white Teflon seal and thought I had found the problem. After teardown I found out the seal was from the reverse feed and reverse seemed to be OK. What I did find is the forward clutches burned up. This trans came in with 3rd clutches burned.

During original rebuild we installed a master overhaul kit including pistons and seals, we also did the Sonnax updates for the valve body with a Sonnax Sure Cure kit and accumulator updates. I have checked the forward piston housing checkball and it seals good. It seals to me that I must have a leak in the feed to the forward clutch or poor line rise but we did install the Sonnax pressure booster kit also. What am I missing on this one? Thanks

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tranibob
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Re: 98 Chevy 4L60E Burnt Forward Clutches ARB

Post by tranibob » Fri Jan 24, 2014 6:27 pm

Lots of bad brand new GM PCS on those right out of the box. Is it still in the vehicle so we can do some testing or is it on the bench?

Did you check the forward piston to make sure it is not cracked if it's the aluminum style?
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barrycole
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Re: 98 Chevy 4L60E Burnt Forward Clutches ARB

Post by barrycole » Fri Jan 24, 2014 6:54 pm

Is the inner bore $%%^%$ in the stator and are the bushings done?
Barry Cole Toronto, Ontario, Canada. Retired after 35 years

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tschafers
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Re: 98 Chevy 4L60E Burnt Forward Clutches ARB

Post by tschafers » Fri Jan 24, 2014 9:52 pm

It's now apart on bench and we had tested, cleaned and reused original PCS. We replace piston with new one and leak tested the piston housing checkball. The forward clutch was not burned originally just the 3/4 clutches.

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Re: 98 Chevy 4L60E Burnt Forward Clutches ARB

Post by tranibob » Fri Jan 24, 2014 11:13 pm

OK, so too late for the pressure gauge.

Check to see if the support shaft is grooved like someone else suggest and make sure the forward air check prefect when applying air in the shaft itself with no leak at the base where the shaft is pressed in the drum.

You said you replaced the forward piston during original rebuilt, was it broken?

Did you go back in with a steel molded piston or with an aluminium piston like it had?
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tschafers
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Re: 98 Chevy 4L60E Burnt Forward Clutches ARB

Post by tschafers » Sat Jan 25, 2014 12:51 pm

We replaced the alum piston with a steel and it got all new bushings but I will clearence on stator support bushings on Monday. I did check make sure input shaft was not leaking but will recheck it also Monday.

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Re: 98 Chevy 4L60E Burnt Forward Clutches ARB

Post by tranibob » Sun Jan 26, 2014 10:26 pm

Did you replace both the forward and the coast clutch piston with steel ones and the later style return spring assembly? I can't remember which one right now, but if you replace only one of the two with Steel you end up with problems. Drawing a blank right now as to if it is the forward or the coast clutch.
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