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Thread: 4L80E No Reverse!

  1. #1
    Join Date
    Aug 2007
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    4L80E No Reverse!

    Basically I lost 3rd and reverse so I tore it down and did a complete rebuild.
    Now I just have no reverse, 3rd works just fine.

    The weird thing is 3rd and reverse use the same clutch pack....so Im at a loss.
    I have good pressure readings in all gears including reverse, fluid is not low either.

    Hopefully some trans experts will see this and know whats the problem....
    89' GMC RCSB 6.0L LQ4, T56, 4.56 Gears

  2. #2
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    That's an old trans and a call back for me so I'll try to help iffen I cans.

  3. #3
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    Quote Originally Posted by GasGuzzler View Post
    That's an old trans and a call back for me so I'll try to help iffen I cans.
    Is there any GM service manuals that show the hydraulic fluid flow for the 80e, I have them for a 700r4 but thats back when I worked at the dealership?
    89' GMC RCSB 6.0L LQ4, T56, 4.56 Gears

  4. #4
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    There are but range reference will help you more. I'll try to take a shot at it tomorrow if you still need help.

  5. #5
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    no reverse...

    Case - rear band anchor pin broken or not positioned
    Center support - leaking at case or broken
    Center support seal leaking
    Center support bolt loose, broken or feed hole blocked
    Rear band broken worn or not anchored
    Rear band apply pin broken worn or not anchored
    Rear servo piston binding in case, seal leaking, damaged or worn
    servo cover gasket leaking or displaced
    servo cover damaged or bolts missing
    Check ball missing
    See my truck data in the "My Garage" section here... http://www.ls1truck.com/forums/my-ga...tml#post191709

  6. #6
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    Crap....you put that odd ball 12-point bolt back in?

  7. #7
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    Quote Originally Posted by Kros383SS View Post
    Basically I lost 3rd and reverse so I tore it down and did a complete rebuild.
    Now I just have no reverse, 3rd works just fine.

    The weird thing is 3rd and reverse use the same clutch pack....so Im at a loss.
    I have good pressure readings in all gears including reverse, fluid is not low either.

    Hopefully some trans experts will see this and know whats the problem....

    things you could have checked before rebuilding when losing reverse and third...

    Solenoid "B" in the valve body. Stuck "off" condition. leaking seals. burned out, no voltage, no signal from PCM, loose connection.
    2-3 shift valve item 312
    See my truck data in the "My Garage" section here... http://www.ls1truck.com/forums/my-ga...tml#post191709

  8. #8
    Join Date
    Aug 2007
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    Quote Originally Posted by GasGuzzler View Post
    There are but range reference will help you more. I'll try to take a shot at it tomorrow if you still need help.
    Yep I need all the help I can get...

    Quote Originally Posted by RedHeartbeat View Post
    no reverse...

    Case - rear band anchor pin broken or not positioned
    Center support - leaking at case or broken
    Center support seal leaking
    Center support bolt loose, broken or feed hole blocked
    Rear band broken worn or not anchored
    Rear band apply pin broken worn or not anchored
    Rear servo piston binding in case, seal leaking, damaged or worn
    servo cover gasket leaking or displaced
    servo cover damaged or bolts missing
    Check ball missing
    Must have got this from the ATSG manual........ I have been over that list of causes for NO Reverse but still cant figure out why just no reverse seeing that NO third gear shares most of those causes.....
    89' GMC RCSB 6.0L LQ4, T56, 4.56 Gears

  9. #9
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    GM Service Information actually has a "No Torque in Reverse and Third" chart and a "No Reverse" chart. Here's the latter...

    No Reverse
    Checks
    Cause

    Case (7)
    The rear band anchor pin is broken or the pin is not positioned.

    Center Support (640)
    Leaking at the case, or the support is broken.

    Center Support Seal (639)
    Leaking

    Center Support Bolt (25)
    • The bolt is loose or broken.

    • The feed hole is blocked.

    Rear Band (657)
    Broken, worn, or not anchored

    Rear Band Apply Pin (73)
    The pin is too short or the pin is binding in the case.

    Piston (65)
    Binding in the case

    Seal (66)
    Leaking, damaged, or worn

    Gasket (63)
    Damaged or displaced

    Cover (62)
    Damaged

    Bolts (61)
    Broken, loose, or missing

    Checkball
    Missing

    Fluid Pressure
    Too low

    Direct Clutch Components

    •Reaction Plates (618)
    The splines are worn.

    •Friction Plates (611)
    The splines or the friction are worn.

    •Spring Assembly (607)
    Jammed

    •Housing (623)
    Cracked

    •Piston (619)
    Leaking

    •Seal (620, 621, 622)
    Leaking

    •Ball Check
    Leaking



    Now for range reference.









  10. #10
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    Quote Originally Posted by RedHeartbeat View Post
    things you could have checked before rebuilding when losing reverse and third...

    Solenoid "B" in the valve body. Stuck "off" condition. leaking seals. burned out, no voltage, no signal from PCM, loose connection.
    2-3 shift valve item 312
    Doesnt have any solenoid's anymore, coverted to full manual. I lost 3rd and reverse after leaving the 3-4 shift valve and spring out when I was going through the VB trying to figure out why 2nd gear would not hold above 3500 RPM.
    After that I lost 3rd and reverse, so I tore it down and found the direct clutches burnt along with the Int. Band which looks like it was skipping on the drum. The 4th clutches looked ok but there was burnt spots on the steels.

    I have good pressure so Im assuming I have good pressure to the Reverse circuit but the band is not engaging.
    Only problem with that is I have 1st gear which also uses the rear band and low/reverse piston.
    3rd gear works fine so Im also assuming the direct clutches are engaging.

    Im thinking real hard on this one before I pull the trans and it could be something in the VB or the rear apply piston.

    Also after the rebuild Im getting close to 300 psi when I give it gas, Its vacuum modulated now. Didnt do that before.
    Park, N, D idle psi-175 quick tap on the gas gives 300psi
    Reverse idle psi-150 quick tap on gas 300 psi.

    I was hoping to get my hands on some fluid flow diagrams so I can see whats going on in each gear.

    I have the range ref. in the ATSG book which helps me somewhat.....
    89' GMC RCSB 6.0L LQ4, T56, 4.56 Gears

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