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Thread: 4L80E 4rth Gear problem

  1. #1
    New Member almusafir's Avatar
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    Default 4L80E 4rth Gear problem

    I have to face one problem from 7/8 days...
    in Transmisasion 4L80E We overhaul it...
    now the problem in 4rth Grear

    I have this Transmission in GMC Truck 454 Engin Model 1990.

    Shifting is OK.. But
    When It became in 4rth Gear and I press the full accelator the care take the kick down and become in 3rd... then its runing in 3rd.. never became 4rth until you stop the car. and switch off the Car..

    Can you please help me for this..

  2. #2
    Joe (Moderator) joecar's Avatar
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    Almusafir,

    Welcome to the forum...

    Please post your .tun file (do Go Advanced->Manage Attachments, and then Browse, Upload).

    When this condition is present (no 3-4 shift after 4-3 WOT), do you get these shifts:
    - 3-2 kickdown (WOT)
    - 3-2 part throttle (PT)
    - 2-1 PT
    - 1-2 PT
    - 2-3 PT

    If you get thes other shifts, then possibly the 3-4 shift valve may be sticking.

    Attached page is from the 4L80E Technician's Guide.

    When this condition is present, monitor the GM.GEAR and use the BiDirectional controls to command 1st, 2nd, 3rd, 4th;
    does GM.GEAR show each of these being commanded...?
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    Last edited by joecar; February 28th, 2007 at 03:48 AM.

  3. #3
    Joe (Moderator) joecar's Avatar
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    Default No Fourth Gear - D4 (from the service manual)

    Checks Cause

    Fourth Clutch Components
    • Seals (527) (531) Nicked or cut
    • Cup Plug (530) Missing
    • Bolt (26) Loose, broken, or missing
    • Piston (528) Jammed
    • Spring Assembly (532) Jammed
    • Retainer Ring (523) Not seated
    • Friction Plates (525) Worn or burned
    • Reaction Plates (526) Worn splices
    • Housing (529) Damaged or cracked
    Overrun Clutch Components
    • Housing (504) Broken
    • Reaction Plates (508) Worn splines
    • Sun Gear (650) Worn
    • 1-2 Solenoid (313) Stuck Off, Pinched wire, O-ring failure, No voltage to the solenoid
    • PCM No signal to the solenoid, Failed
    • 3-4 Shift Valve (308) Stuck
    Check the PCM for current DTCs.
    Last edited by joecar; February 28th, 2007 at 03:59 AM. Reason: This was a nice table in html, but it isn't being interpreted right...?

  4. #4
    Joe (Moderator) joecar's Avatar
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    I assume you are using a Gen III/IV PCM and have fitted the necessary hardware to your 454 for the PCM to operate the engine and transmission...

    Which part of my assumption is incorrect...?

  5. #5
    New Member almusafir's Avatar
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    Quote Originally Posted by joecar
    Almusafir,

    Welcome to the forum...

    Please post your .tun file (do Go Advanced->Manage Attachments, and then Browse, Upload).

    When this condition is present (no 3-4 shift after 4-3 WOT), do you get these shifts:
    - 3-2 kickdown (WOT)
    - 3-2 part throttle (PT)
    - 2-1 PT
    - 1-2 PT
    - 2-3 PT

    If you get thes other shifts, then possibly the 3-4 shift valve may be sticking.

    Attached page is from the 4L80E Technician's Guide.

    When this condition is present, monitor the GM.GEAR and use the BiDirectional controls to command 1st, 2nd, 3rd, 4th;
    does GM.GEAR show each of these being commanded...?
    Thanks Sir...

    But still same problem..

    it appear code no 68

  6. #6
    Joe (Moderator) joecar's Avatar
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    I don't have an early GM manual with me right now, what does DTC 68 mean...?

    Oh, you're using the OBD-I ECM.

  7. #7
    Lifetime Member Biggsy's Avatar
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    Off the top of my head I believe code68 is a trans slip fault

    Cheers,
    Dave.

  8. #8
    New Member almusafir's Avatar
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    Quote Originally Posted by joecar
    I don't have an early GM manual with me right now, what does DTC 68 mean...?

    Oh, you're using the OBD-I ECM.
    Yes...

    I 'm using OBD-I ECM..

    I think Code
    68 means

    Cruise control - system
    circuit problems.
    OR
    Air Conditioner (A/C)
    clutch relay - short circuit.
    OR
    (Transmission) Overdrive
    ratio error - engine RPM
    greater than input speed.

  9. #9
    New Member almusafir's Avatar
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    Quote Originally Posted by Biggsy
    Off the top of my head I believe code68 is a trans slip fault

    Cheers,
    No Sir code68 appearing...
    Transmission Shifting is fine and OK.. But when you became 4rth Gear and you press full accelator it takes Kick down and coming in 3rd... Then it never change of 4rth.. until you stop and switch off the car..
    When you shitch off the car and start is again its ok in normal

  10. #10
    Joe (Moderator) joecar's Avatar
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    "Overdrive ratio error" means the fourth clutch is not applying;

    when the fourth clutch is applied, it holds the overdrive sun gear stationary which causes the overdrive carrier assembly to "overdrive" the forward clutch housing (where the input speed is measured).

    Edit: if the fourth clutch is slipping or not applying, then the input speed measured at the forward clutch housing will be wrong, and the PCM raises the code.

    See the blue, red, gold components in the next post...

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