C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Transmission Problem

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Old Sep 11, 2011 | 08:25 AM
  #1  
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Default Transmission Problem

I just got my unit rebuilt and reinstalled. I also replaced the torque convertor with a higher stall unit. I drove it for the first time, went about 5 miles, and it worked great until I was getting home. Pulling into the driveway it started acting like it was slipping in first gear and did not move in reverse. I put it back up on the lift and pulled the pan. Don't see any loose linkage etc.

Any thoughts?
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Old Sep 11, 2011 | 08:39 AM
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Sounds like you need to get it towed back to the rebuilder. Good luck...
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Old Sep 11, 2011 | 10:28 AM
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Was the TV - Throttle Valve cable adjusted correct on your 1991 C4 700R4 Transmission when it was reinstalled ?

Sounds like a low line pressure issue to begin with.
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Old Sep 11, 2011 | 10:37 AM
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Yes, TV cable was correct.
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Old Sep 11, 2011 | 10:45 AM
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OK.

Strange problem because you lost 1st & reverse at the same time.

1st is Fed from the rear of transmission case oil circuit.

Reverse is fed down through the stator shaft assembly to the reverse input drum assembly.

Last edited by 87 vette 81 big girl; Sep 11, 2011 at 11:18 AM.
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Old Sep 11, 2011 | 10:51 AM
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Need to check the TV cable operation from down below the car.
Make sure the Throttle valve internal plunger is releasing fully each time.

There was a special adjustment procedure on 1991's for the TV cable.

Check in your FSM.

If OK,
then check the forward & reverse boost valve assembly.
Accessible from underneath with the transmission pan off.

Need a very good pair of small internal snap ring pliers to remove the small True Arc style snap ring retainer.

Be careful not to drop the Boost valves on the garage floor & have them roll away to Tim Buck 2.

Something is hanging up somewhere causing low line pressure.
Dirt or a metal burr.

Line bias valve may stuck also.
Small roll pin punches required & lots of patience too.

Brian
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Old Sep 11, 2011 | 03:28 PM
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I took the valve body off and checked for movement on all the internal valves. Everything seemed to be fine. I put it all back together and now it seems to be fine. I guess there was some trash somewhere in the unit that caused something to hang up. Thanks for all the input.

Chuck
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Old Sep 11, 2011 | 04:38 PM
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You moved the TV valve & line bias valve around then & freed them up each.

Glad it was a simple fix for you.

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Old Sep 11, 2011 | 11:06 PM
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A new torque converter and a fresh tranny need to have to oil level checked a couple of times. A new converter will drink tranny fluid during the first few minutes. If the level is low, the tranny will slip (done that).
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