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Thread: Hard-shifting 4L80E

  1. 10-05-2007, 12:44 #1
    Rondane
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    Default Hard-shifting 4L80E

    Hi all, have a problem with the transmission in my -91 burb. Started a couple of weeks ago with harsh shifts from 1. to 2. gear. Rpm was also higher than normal when it banged into second gear and lock-up was`nt engageing when it should. Then suddenly everything went back to normal with smooth shifts. But of course, troubles came back and today it was almost impossible to get the lock-up engaged. Transfluid and filter are about 10000 miles old, on the mark and nice color. I think (hope) its a electrical problem, what do you guys think? Solenoid in the pan? Tps?

    Trond
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  2. 10-05-2007, 14:08 #2
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    Didn't reallize they used the 4L80E on the '91s...

    Could be the TV switch. Check for codes, too.
    The Constitution needs to be re-read, not re-written!

    If you can't handle Dr. Seuss, how will you handle real life?

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  3. 10-05-2007, 16:10 #3
    Rondane
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    Hi John, this tranmission was introduced in -91 behind 6.2- and 454-engines.
    About the TV-switch, is this short for trottlevalve switch? Is this in any way connected with the TV-cable? If thats so I`am not sure if I have a TV-cable on my transmission. Correct me if I`am wrong.

    Trond
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  4. 10-12-2007, 01:44 #4
    DA BIG ONE
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    Default Trouble shooting 4L80

    I'm thinking the 4L80 transmission is hard to come by in your area it maybe a good idea to get tech manuals and parts for it, see attached link. http://www.transmissionspecialty.com/

    The euro's strength can get you a good deal on an imported unit from North America if you decide to go this way make sure you get 1999 or later unit as it will have all the updates to correct problems associated with older units like you have.
    99 GMC SUB, 2500, 4x4, 6.5 TD (F) #H32 enhanced blk, Phaser timing set, B&D IC, 3" ATS exh, K&N w/prefilter, 4WD NVG 246, 4L80E kevlar Transgo off road/tow mods/B&M supercooler, 14 FF MagTec w/locker 3.42:1, 9.25" IFS frt/diff 3.42:1 w/ARB locker, AutoMeter Boost & pre-turbo pyro meter, 12,000 lb hydro winch, Warn classic bumper w/brushguard & diesel scoop, Max E-torq Stage 3, hi pop inj, oil bypass sys, on board air comp for front ARB locker & tire inflation, DynaView driving/auto-cornering lts, DZ nerfs, A/T 285/75/16 SilentArmor 3750 lb rated on 3750 lb rated Alcoa, 3 IP drivers 2 r spares.
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  5. 10-12-2007, 08:31 #5
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    What series of truck, 1500, 2500 ? which engine?

    Does the tranny have a cable coming from the case near the dipstick tube?

    Robyn
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  6. 10-13-2007, 04:59 #6
    Rondane
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    Hi, my truck is a 2500 series with a 6.2 diesel. And yes Robyn, a cable is comming up near the dipstick tube with wires to the TPS and some to the IP.

    Trond
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  7. 10-13-2007, 07:51 #7
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    If it has a cable up by the dipstick then your truck has a 700R4 tranny and not a 4L80

    The 700 pan is almost square and will have a small square electrical plug on the LH side of the pan rail about midway back.

    The hard shifting is most likely a throttle pressure issue.
    Check the cable where it connects to the IP and be sure it moves freely.
    If the cable has become stuck it will cause hard shifts at light throttle.

    Let us know what you find
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  8. 10-13-2007, 09:19 #8
    Rondane
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    Hi Robyn, I guess I should know better than arguing with you, but I`ll give it a shot. When you asked about the cable by the dipstick tube I thought you ment elecrical wires. My technical English is not that good. There is a plastictube, about 1 inch in diam. comming up by the tube, it is black and have a bunch of wires inside. My pan have 17 bolts and when I change transfluid and filter I replace it with a 4L80E filter. There is no cable attatched to the transcase, only two places where electric wires are connected. One of these is covered with a plastic shield with a torxscrew in the middle. I hope this will convince you.

    Trond
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  9. 10-13-2007, 14:48 #9
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    OK then you do have a 4L80
    During this time frame the 6.2 could have been installed in a light duty 2500 with a 700R

    Can you scan the ECM to see if there are any codes?

    The next thing to check is to be sure the TPS is working correctly. If the TPS is giving a bad reading it can cause the harsh shifts..

    let us know

    Good luck
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  10. 10-15-2007, 01:45 #10
    Rondane
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    Hi all, just scanned for codes. Got me a 85 and 86. Am I in big trouble or is it just some sensors? What does it mean: "TCC is mechanically stuck on" ?



    85 Programmable Read Only Memory error or undefined
    gear ratio (input or output sensor failure)
    Torque converter clutch (TCC) - TCC is mechanically
    stuck on

    86 Analogue/Digital Electronic Control Module (ECM)
    error or shift Solenoid "B" stuck on

    Trond
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  11. 10-24-2007, 11:24 #11
    Rondane
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    Hi all, is it absolutely certain that the TPS will throw a code if its broken?

    Trond
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  12. 10-24-2007, 12:20 #12
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    The TPS has 3 redundant circuits. The PCM monitors all 3 for agreement. I can't conceive of a failure mode that would not set at least one code.
    The Constitution needs to be re-read, not re-written!

    If you can't handle Dr. Seuss, how will you handle real life?

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  13. 10-24-2007, 12:53 #13
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    Arrow

    The APP is the skinny pedal module. The TPS is the switch on the side of the IP. The 91 has a TPS, and 1994+ has an APP (no mechanical IP input).
    1985 Blazer 6.2
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  14. 10-24-2007, 14:17 #14
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    (oops!)

    My comments refer to the APP, not the TPS.
    The Constitution needs to be re-read, not re-written!

    If you can't handle Dr. Seuss, how will you handle real life?

    Current oil burners: MB GLK250 BlueTEC, John Deere X758
    New ride: MB GLS450 - most stately
    Gone but not forgotten: '87 F350 7.3, '93 C2500 6.5, '95 K2500 6.5, '06 K2500HD 6.6, '90 MB 350SDL, Kubota 7510
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  15. 10-28-2007, 11:12 #15
    Rondane
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    Angry

    Hi folks, changed shiftsolenoids today but no improvement. And still getting code 85 and 86.
    No code for the TPS.

    Trond
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