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4L80e in Hummer started slipping when warm....

Discussion in 'All Other Transmissions' started by Sand, Mar 28, 2018.

  1. Sand

    Sand Active Member

    187
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    Mar 27, 2016
    Canada
    My 4L80e in the Hummer just started acting up....
    No codes. Works fine cold. When warm looses OD, then third. Then starts slipping in first and second...
    Fluid is fresh one year ago. 100 000 miles.
    Dipstick is showing fluid. Strangely there is loads of rust at the top of the dipstick....thats new since I last checked it but its been a really wet damp winter.
    Just got home and first code poped
    P0236.
    I had it last week and changed the MAP sensor today. Guess I was wrong for 84 dollars...lol
    Ill search the threads in a couple hours for a similar issue.
    Sand
     
    MrMarty51 likes this.
  2. THEFERMANATOR

    THEFERMANATOR FRANKENBURBAN Staff Member Lead Moderator

    8,978
    2,306
    May 9, 2008
    ZEPHYRHILLS FL
    If it happened suddenly, there's always a chance the filter seal dropped down, and it's sucking air. Or your pressure control solenoid has failed. All you can do is put a pressure guage on it, and see what's going on. Also look at the fluid and see if it looks milky or aerated, if the filter seal goes, the fluid will start frothing, and look milky from all the air bubbles.
     
    MrMarty51 likes this.
  3. Sand

    Sand Active Member

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    Mar 27, 2016
    Canada
    That's good stuff. On the dipstick it looked clear. Ill dtop the pan tomorrow.
     
    MrMarty51 likes this.
  4. WarWagon

    WarWagon Well it hits on 7 of 8...

    8,163
    2,534
    Nov 15, 2009
    AZ
    Rust on the dipstick can indicate coolant leaks like the radiator heat exchanger having a pinhole. A oil sample of the trans oil can rule this out esp. before you ruin a rebuilt transmission. Set sample aside to send in later in case minor fixes don't work.
     
    MrMarty51 likes this.
  5. MrMarty51

    MrMarty51 Well-Known Member

    1,231
    1,094
    Aug 1, 2017
    Miles City, Montana
    P0236 code
    Check the vacuum, clean all terminals at the back of the engine, if it is like the GM400 with several connectors back there.
    I had quite a struggle getting so the truck would not trip that code.
     
  6. Sand

    Sand Active Member

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    Mar 27, 2016
    Canada
    Oil anaysis kit ordered. Thanks.
    Vac guage set aside for me at the parts store.
     
  7. Sand

    Sand Active Member

    187
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    Mar 27, 2016
    Canada
    Cleanest pan ever. Not burnt. Not foamy.
     

    Attached Files:

  8. Sand

    Sand Active Member

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    Mar 27, 2016
    Canada
    Filter is in place. No chunks!
    Now looking for a pressure solenoid and checking wires for obvious issues.
     

    Attached Files:

  9. Sand

    Sand Active Member

    187
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    Mar 27, 2016
    Canada
    This is how it is dropping a pan without even having to jack up the vehicle. Lol
     

    Attached Files:

    Will L. likes this.
  10. Sand

    Sand Active Member

    187
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    Mar 27, 2016
    Canada
    By bellhousing it seems. Screenshot_20180329-124004.png
     
  11. Sand

    Sand Active Member

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    Mar 27, 2016
    Canada
    So is this a "put a new one in and see" game?
     

    Attached Files:

  12. Will L.

    Will L. Well-Known Member

    7,406
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    Jan 25, 2013
    Boulder City Nv
    Hummer do not have the trans fluid go through the radiator. Complete seperate cooler. No way for atf and coolant to exchange. Pickups have a lil cooling stack, hummers have a STACK. Also seperate oil cooler like pickups but larger, a power steering cooler, and of course ac condensor.
     
    WarWagon likes this.
  13. Sand

    Sand Active Member

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    Mar 27, 2016
    Canada
    My first check was transfer case too full. Trans fluid goes through a heat exchanger in there.
    No dice...that would have been too easy.
     
    Will L. likes this.
  14. Sand

    Sand Active Member

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    Mar 27, 2016
    Canada
    Local transmission place lent me a known good pressure solenoid. Swapped it out. No change. Still downshifts and winds out in lower gears. They lent me a output/input speed sensor too. I swapped my input out first. No change. Then swapped my output out....no change...Boo.
     
  15. ak diesel driver

    ak diesel driver 6.5 driver

    12,758
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    Feb 7, 2009
    alaska
    see if they'll let you borrow a pressure guage
     
    WarWagon likes this.
  16. Sand

    Sand Active Member

    187
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    Mar 27, 2016
    Canada
    Sooo. My torque android app is not picking up TCM vodes.
    A proper OBD tool is now showing P0730.
    Thats better.
     
  17. monka

    monka New Member

    9
    7
    Jun 5, 2017
    Ontario
    I'd would have done the full solenoid kit change, it's cheap
    Possibly shift solenoids, but you have some done now, hopefully it not major.

    Lol, this way you've covered most bases, I lost gears, as well (felt like neutral) stop, then it would work again, that kit cured it, now 3 years later all is smooth still,
     
  18. Sand

    Sand Active Member

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    Mar 27, 2016
    Canada
    Nice to hear! Shift solenoids are cheeeap and will be here on the weekend. Thanks.
     
  19. THEFERMANATOR

    THEFERMANATOR FRANKENBURBAN Staff Member Lead Moderator

    8,978
    2,306
    May 9, 2008
    ZEPHYRHILLS FL
    P0730 is an incorrect gear ratio, aka extreme slippage code. My best advice I can give is STOP throwing parts at it, and get a pressure guage on it. Or for a simple test, unplug the main electrical plug from the transmission, and see what it does in limp mode. You should have reverse and 2nd, but if you feel slippage in limp mode, your problem is definately something major inside the trans like a cracked accumulator piston, or busted servo piston.
     
  20. Sand

    Sand Active Member

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    Mar 27, 2016
    Canada
    I know....Im sorry!!!! Im the guy I warn people not to be....Im not a tranny pro yet and have no pressure guage. On my list. Its a long weekend and at my level all I can do is try new parts. So far no investment other than beer for solenoid loan. 50 bucks buys new shift solenoid's as its wed before I can have the thing looked at properly. The pan is off and I know its B grade but Ill try it anyway.
     

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