GM Inside - Ford Inside - Ford Ranger - Jeep - American Muscle

Support FSC and see no ads! - Click Here
Page 1 of 2 12 LastLast
Results 1 to 20 of 27

4L80E, TC lockup erratic

This is a discussion on 4L80E, TC lockup erratic within the Technical / Maintenance forums, part of the General Discussion category; 1992 C2500, 4L80E Fluid looks great, probably less than 10,000 miles on fluid/filter (plan on doing it this weekend). Driving ...

  1. #1
    Registered User
    Join Date
    Sep 2009
    Location
    Michigan
    Posts
    484

    4L80E, TC lockup erratic


    Support FSC and see no ads! - Click Here
    1992 C2500, 4L80E
    Fluid looks great, probably less than 10,000 miles on fluid/filter (plan on doing it this weekend).

    Driving at 70-75 mph in OD the torque convertor does not want to lockup. It will occasionally try, I can hear the RPM drop, but in less than 1 sec it will unlock again. At one point it went thru this lock/unlock cycle roughly 6 times in about 10 seconds.

    Does not seem to matter what the throttle input is. Even letting off to almost a complete coast downhill it won't lockup. Then throttling up a hill it will lock. There just seems to be no rhyme or reason for it, it's completely erratic. If I slow down to 65 mph it locks up and acts fine.

    This was my grandfather's truck, supposibly he had troubles with the tranny on the freeway a few years back. Transmission shop couldn't find anything wrong, and it acted fine after whatever incedent had occured.

    What's going on? Where would you start looking to track this down?

    92 K1500 WT - Gone
    92 C2500 - Current. Scottsdale, 350tbi, 4L80E, 14 bolt sf

  2. #2
    Registered User
    Join Date
    Sep 2009
    Location
    Michigan
    Posts
    484

    Re: 4L80E, TC lockup erratic

    Wow, so far from searching the forum I've come up with people having simular problems that claimed it was caused/cured by:

    Fuel pump going out
    Fuel filter
    Spark plugs
    Plug wires
    Cap
    Rotor
    Ignition module
    Ignition coil
    Coolant temp sensor
    Brake switch
    Dirty trans fluid
    Bad torque convertor, cured by bottle of additive
    Transmission on it's last leg (slipping)
    Bad wiring connection
    Broken wire to trans
    Worn/grounded wire to trans
    Bad computer program
    VSS bad
    ABS bad

    And probably some other's that I can't even remember.

    So far I'm thinking brake switch. This morning it performed perfectly fine, and I tested touching the brake to see if the TCC disengages. It did, but I barely put any pressure on the brake, and swear it didn't even move. If the adjustment is that close I could see it sometimes being "over the edge" and the truck thinking the brake is starting to be pushed.
    Last edited by adam728; 07-22-2010 at 04:26 AM. Reason: Can't spell at 6:45 am

    92 K1500 WT - Gone
    92 C2500 - Current. Scottsdale, 350tbi, 4L80E, 14 bolt sf

  3. #3
    Registered User
    Join Date
    Sep 2009
    Location
    Michigan
    Posts
    484

    Re: 4L80E, TC lockup erratic

    Another update, for any of the 64 viewers that may care. I'm about 90% certian it's the brake switch. I got the trans to act up on the way home tonight and stopped it when I pulled up on the brake pedal with my toe. I could get the tc to unlock with barely any pressure on the pedal, in almost any direction except up. Even lightly pushing on the side would unlock the torque convertor, then lifting it with my foot would get it to lock up again.

    I'll try and pick up a new one this weekend and replace it, I'll update next week if it truely was my cure (I hate posts about problems that never give the solution, doesn't help those searching!!).

    92 K1500 WT - Gone
    92 C2500 - Current. Scottsdale, 350tbi, 4L80E, 14 bolt sf

  4. #4
    Registered User TanTahoe's Avatar
    Join Date
    Jun 2006
    Location
    Michigan
    Age
    29
    Posts
    787

    Re: 4L80E, TC lockup erratic

    My 4L60E did something like this, It was just a break switch going bad.
    1995 Tahoe: 4L80E swap; Started Solid Axle Swap
    Freedom Isn't Free

  5. #5
    GMC RULZZ NEUMANNZZ's Avatar
    Join Date
    Mar 2005
    Location
    San Diego
    Age
    47
    Posts
    19,987

    Re: 4L80E, TC lockup erratic

    check the brake pedal return spring
    Last edited by NEUMANNZZ; 07-22-2010 at 06:12 PM.
    O2 GMC RCSB 4.8L V8 AUTO 3.73's
    rebuilt/beefed up 4L60E(at 43,000miles)
    Matching Ninja 500r


  6. #6
    Registered User
    Join Date
    Sep 2007
    Location
    Hazel, KY
    Posts
    881

    Re: 4L80E, TC lockup erratic

    hope its only the brake switch
    the torque converter in my 2000 model 2500 series with 4l80e when bad.

    you could turn motor off for a 20 sec period and then it would work again for a while, but was only getting worse. reset computer
    had to replace torque converter and all was fine. it had sometype of seal broken and would not hold the oil pressure.

    watch repairmen on this repair: most wanted to rebuild trans and there was nothing wrong with trans.
    you need to find a mech that will take the time to give you a full diagnosis of the problem, after talking with about 6 repair shops i found a guy who pulled dip stick, looked at oil, smelled oil, put oil on white paper and said he did not think trans was bad.

    then drove truck with a snapon meter attached to port.

    when i when to pickup truck there was another 2000 model 2500 series there with the same problem
    cost me about $1000 for the repair.

  7. #7
    Registered User
    Join Date
    Sep 2004
    Location
    souhtern NH
    Posts
    30

    Re: 4L80E, TC lockup erratic

    I hope it's your brake switch. If it is it will save you a ton of money. I had the same problem with my 93 K1500. Mine did the lock/unlock/lock deal every time I went over a bumpy spot in the road. I described the problem excatly to the "highly regarded" tranny shop owner. He said it sounded electrical to him and sent me to the auto electrics place. They drove it around with a scanner and no codes or faults (duh!!!). They sent me back to the tranny shop and the guy said I should have it rebuilt since it had over 100K on it. $1500 later I pick the truck up, drive out of his lot and get 1/2 mile down the street and it does it again. I spin around, pissed, and take it back. He tears it down again and replaces the wiring harness, the only part he didn't replace the first time. I pick it up again and get 3/4 of a mile from his shop and it locks/unlocks again. I turn around and take it back again. This time he puts his best guy on it. He says, "Hmmmm, I saw this once before" and diagnoses it as a misadjusted brake switch. Problem fixed! It only cost me $1500 and a couple weeks w/o my truck and about 150 miles driving back and forth to the shop. This happened before I started reading and subscribing to message boards for the cars I own. I NEVER would've taken that truck in if I had looked around on the net. I even asked the guy "What controls the torque converter lock-up?" and he told me the computer did. If I'd thought about it for a little I would've figured it out for myself.

    PS: The tranny is dead again with about 30K on the rebuild. Too much time has passed and he won't warranty it. Screw it, I'll swap it out myself this time.
    Last edited by granitestategn; 07-27-2010 at 05:03 PM. Reason: spelin air
    Gregg

    1993 GMC K1500 Ext.Cab
    1997 Saab 9000 Aero 2.3L Turbo 5-spd
    1997 Saab 9000 CSE 2.3L Turbo Auto
    1994 Saab 9000 Aero 2.3L Turbo 5-spd
    1987 Buick Grand National 12.98@104
    1998 Subaru Legacy GT Wagon
    1993 Saab 9000 CSE 2.3L Turbo 5-spd

    .....too many cars, not enough turbos

  8. #8
    Registered User dave89iroc's Avatar
    Join Date
    Sep 2007
    Location
    SE Michigan
    Age
    36
    Posts
    4,815

    Re: 4L80E, TC lockup erratic

    Quote Originally Posted by maxwell1 View Post
    hope its only the brake switch
    the torque converter in my 2000 model 2500 series with 4l80e when bad.

    you could turn motor off for a 20 sec period and then it would work again for a while, but was only getting worse. reset computer
    had to replace torque converter and all was fine. it had sometype of seal broken and would not hold the oil pressure.

    watch repairmen on this repair: most wanted to rebuild trans and there was nothing wrong with trans.
    you need to find a mech that will take the time to give you a full diagnosis of the problem, after talking with about 6 repair shops i found a guy who pulled dip stick, looked at oil, smelled oil, put oil on white paper and said he did not think trans was bad.

    then drove truck with a snapon meter attached to port.

    when i when to pickup truck there was another 2000 model 2500 series there with the same problem
    cost me about $1000 for the repair.
    same with my 2000 2500, replaced the convertor, all fixed
    ASE Master Certified Technician

    2000 Silverado 6.0 4L80E 2wd
    *RIP*1994 Z71 SCLB 355, Dart Heads, 10.5:1 CR, PM rods, CC XR270HR

  9. #9
    Registered User 2500ak's Avatar
    Join Date
    May 2007
    Location
    Alaska
    Age
    25
    Posts
    2,525

    Re: 4L80E, TC lockup erratic

    There are a few possibilities here. The 4l80e, when it gets very old has a TCC problem caused by a valve that wears its bore and causes pressure to leak past. This will cause a shudder, and eventually a clutch failure. Sonnax has a kit that reams out the bore and installs a modified valve that never does that again.

    It could be the clutch is bad.

    Could be the break switch.

    It could also be a random missfire, have the engine checked for stored codes.

    Could also be a solenoid.
    Last edited by 2500ak; 07-27-2010 at 05:47 PM.

    Transgo HD2 | Magnaflow DI/DO | CAI | BlackBear Tune| Dual Optima Red Tops: 2000 Cold Craking Amps | Denali Projectors |

  10. #10
    Registered User
    Join Date
    Sep 2009
    Location
    Michigan
    Posts
    484

    Re: 4L80E, TC lockup erratic

    No codes, no shudder, truck seems to run dead smooth.

    Hoping it's the brake switch. I adjusted it and it seemed to fix it, but I'm going to throw a new one in to make sure it's not acting up. Planned on doing it this weekend, but rushed to the hospital instead. I wasn't supposed to become a dad for 2 more weeks, but no one told the kid that!

    92 K1500 WT - Gone
    92 C2500 - Current. Scottsdale, 350tbi, 4L80E, 14 bolt sf

  11. #11
    Registered User
    Join Date
    Sep 2009
    Location
    Michigan
    Posts
    484

    Re: 4L80E, TC lockup erratic

    Brake light switch was the culprit.

    As I said before, I could just BARELY touch the brake pedal and the TC would unlock. I did the switch adjustment, and everything looked fine, but still any pressure on the pedal unlocked the convertor. With the new switch I have to move the pedal a good 1/4 inch before it triggers and unlocks the convertor. I'm guessing the contacts in the old one were just getting worn out.

    DONE!

    92 K1500 WT - Gone
    92 C2500 - Current. Scottsdale, 350tbi, 4L80E, 14 bolt sf

  12. #12
    Registered User
    Join Date
    Jul 2010
    Location
    Lehigh Valley, PA
    Posts
    63

    Re: 4L80E, TC lockup erratic

    i have a 2000 crew cab 2500 350 with the 4l80e. recently drove from pennsi where i live to virginia. converter was locked solid and wouldnt unlock jus about wen i got there. put the truck manually into 3rd and it came out but i lost overdrive and it wouldnt lock up again. the shifts from a dead stop than were very firm and i had to run the rpms up alittle before it would shift and the converter still wouldnt lock up. turned the truck off. let it sit for 5 minutes and drove it again and everything was fine. drove the truck home 4 days later and went about 150 miles no problem. got somethin to eat and kept goin and when i was almsost home goin up a hill i got stuck behind a tractor trailer and the converter wouldnt unlock and i was doin 30mph in overdrive! manully pulled it into 3rd and than it shifted firm again and wouldnt lock up. got home and unloaded everything and went to put fuel in it and everything was fine again... is this a similar problem??

  13. #13
    Registered User 2500ak's Avatar
    Join Date
    May 2007
    Location
    Alaska
    Age
    25
    Posts
    2,525

    Re: 4L80E, TC lockup erratic

    Quote Originally Posted by 2000crewcabOBS View Post
    i have a 2000 crew cab 2500 350 with the 4l80e. recently drove from pennsi where i live to virginia. converter was locked solid and wouldnt unlock jus about wen i got there. put the truck manually into 3rd and it came out but i lost overdrive and it wouldnt lock up again. the shifts from a dead stop than were very firm and i had to run the rpms up alittle before it would shift and the converter still wouldnt lock up. turned the truck off. let it sit for 5 minutes and drove it again and everything was fine. drove the truck home 4 days later and went about 150 miles no problem. got somethin to eat and kept goin and when i was almsost home goin up a hill i got stuck behind a tractor trailer and the converter wouldnt unlock and i was doin 30mph in overdrive! manully pulled it into 3rd and than it shifted firm again and wouldnt lock up. got home and unloaded everything and went to put fuel in it and everything was fine again... is this a similar problem??
    Firm shifts usually mean the trans has detected a slipping condition of some kind (this can be anything from a bad sensor, or the TCC not locking, to slipping clutches), and it maxes the Adaptive Shift pressures. Or the trans could be shifting with the TCC engaged, it isn't supposed to do this the PCM commands it to unlock during shifts.

    Not sure what would make it not unlock though. Maybe something like a dead break switch, or a failed solenoid / stuck TCC reg valve in the VB.

    Transgo HD2 | Magnaflow DI/DO | CAI | BlackBear Tune| Dual Optima Red Tops: 2000 Cold Craking Amps | Denali Projectors |

  14. #14
    Registered User
    Join Date
    Jul 2010
    Location
    Lehigh Valley, PA
    Posts
    63

    Re: 4L80E, TC lockup erratic

    its weird. its only happened to me when i drove the truck over 200 miles straight. but when i pull it manully out of overdrive it unlocks but wont lock back up. than it wont shift into overdrive but i never ran the rpms up to get it back in again like i did the other gears. shut if off and start it and it runs fine. if anything sensor wise would be bad it would throw a CEL? i been drivin the truck since i got back and all is fine. also when i was down in virginia i ran first gear out to 4400 and it started makin some kind of bangin noise for less than a second cuz i let out and it shifted. the "two speed" like 3rd gear seemed to slip a little as well when i got into the throttle a little. my guess is the converter leaks after the fluid gets hot and it stays in one gear for a prolonged time. the truck was a plow truck for a little before i got it and the plow was removed and i ran it another 14000 since i had the thing so who knows the last time the fluid and filter was changed. im gonna change it tomora and see what the filter and fluid look like. its a dark red on the stick and doesnt have that sweet smell to it. more of a worn out somewhat burnt smell.

  15. #15
    Registered User 2500ak's Avatar
    Join Date
    May 2007
    Location
    Alaska
    Age
    25
    Posts
    2,525

    Re: 4L80E, TC lockup erratic

    Quote Originally Posted by 2000crewcabOBS View Post
    its weird. its only happened to me when i drove the truck over 200 miles straight. but when i pull it manully out of overdrive it unlocks but wont lock back up. than it wont shift into overdrive but i never ran the rpms up to get it back in again like i did the other gears. shut if off and start it and it runs fine. if anything sensor wise would be bad it would throw a CEL? i been drivin the truck since i got back and all is fine. also when i was down in virginia i ran first gear out to 4400 and it started makin some kind of bangin noise for less than a second cuz i let out and it shifted. the "two speed" like 3rd gear seemed to slip a little as well when i got into the throttle a little. my guess is the converter leaks after the fluid gets hot and it stays in one gear for a prolonged time. the truck was a plow truck for a little before i got it and the plow was removed and i ran it another 14000 since i had the thing so who knows the last time the fluid and filter was changed. im gonna change it tomora and see what the filter and fluid look like. its a dark red on the stick and doesnt have that sweet smell to it. more of a worn out somewhat burnt smell.
    Slipping in OD is what kills most transmissions, but on the 4L80e it's 3rd (unless the reverse band snaps anyway). In stock form they just don't apply enough pressure to it, it's 60psi iirc. That's probably the biggest thing that the Transgo HD2 shiftkit fixes, triples it to a much more robust 180psi.

    The only fluid mechanical problem common with the converters is the TCC regulator valve that can wear out, and allow fluid to slip past it. This can make the trans do strange things. Usually slipping, or shuddering are the two main symptoms. Since your trans is firming up the shifts I'd suspect this is at least part of the problem. Also it can lead to pressure spikes (another thing most shiftkits fix by adding a bleed valve in the circuit like a transgo, and some other brands have ones that are integrated into the reg vale itself, I think), which can actually crack the valve body or the case and damage other components too. If the converter is erratically operated and fed pressure long enough the clutch does fail.

    You can have a bad senor and not have a code thrown for it. The comp isn't always good at deciding what is a normal reading and what isn't.

    Burnt smell = burnt fluid. This either means it overheated, or the clutches are going bad. If you don't find a lot of material in the pan (and I mean a lot because 80e's tend to shed quite a bit over the course of their lifetime), and as long as there are no big chunks of clutch or metal, and you're under 140,000mi you might consider a shiftkit and that sonnax TCC regulator fix kit. It's kind of a gamble because it may already be in rebuild territory.

    How many miles have you got on it again?

    This is the HD2 shiftkit, it really beefs up the 80e and shores up most of the problems that cause them to fail. Not hard to install, just a bit time consuming. If you're going to change the fluid and filter you're in there anyways. Just something to consider.
    http://www.summitracing.com/parts/TRG-4L80E-HD2/

    I did a Tech article on how to install one of these:
    http://www.fullsizechevy.com/showthr...ransgo+install

    Make sure you use Torlon checkballs too

    This may or may not fix the slipping 3rd depending on state of the clutch.

    Sonnax 34994-18K is the part number of the kit that fixes the TCC worn bore condition. I've been meaning to put one of these in as a preventative measure, just haven't gotten around to it yet
    http://sonnax.com/part_summary.php?id=4975&pl=3

    If not, I'd just get ready to have it rebuilt then beef it up with the SK, and the reg valve upgrade afterward. Run synthetic Dex VI (dexron 6) fluid and adding a good cooler would help too.

    Transgo HD2 | Magnaflow DI/DO | CAI | BlackBear Tune| Dual Optima Red Tops: 2000 Cold Craking Amps | Denali Projectors |

  16. #16
    Registered User
    Join Date
    Jul 2010
    Location
    Lehigh Valley, PA
    Posts
    63

    Re: 4L80E, TC lockup erratic

    thanks alot pal . i drove it today and the trans was fine, for a little. i was in OD on the highway and the converter wouldnt lock up about 20 min after i was drivin it. never had any of the other symptoms i stated before. after the converter wouldnt lock up and kept slippin in all gears the motor started a bad missfire but thru no code. needless to say i drove it home and parked it. i never got a chance to change the fluid or pull the pan so im not sure about what anything in there looks like. not sure why the motor started missing and actin up but the truck pretty much had the power of a prius. any suggestions on what i got goin on now?? and im at about 100,900 miles on the truck.
    Last edited by 2000crewcabOBS; 08-05-2010 at 06:38 PM.

  17. #17
    Registered User 2500ak's Avatar
    Join Date
    May 2007
    Location
    Alaska
    Age
    25
    Posts
    2,525

    Re: 4L80E, TC lockup erratic

    Quote Originally Posted by 2000crewcabOBS View Post
    thanks alot pal . i drove it today and the trans was fine, for a little. i was in OD on the highway and the converter wouldnt lock up about 20 min after i was drivin it. never had any of the other symptoms i stated before. after the converter wouldnt lock up and kept slippin in all gears the motor started a bad missfire but thru no code. needless to say i drove it home and parked it. i never got a chance to change the fluid or pull the pan so im not sure about what anything in there looks like. not sure why the motor started missing and actin up but the truck pretty much had the power of a prius. any suggestions on what i got goin on now??
    Ok, a misfire -even a misfire that isn't bad enough to throw a code- will cause the pcm to unlock the converter. That may be part of it.
    Last edited by 2500ak; 08-05-2010 at 06:39 PM.

    Transgo HD2 | Magnaflow DI/DO | CAI | BlackBear Tune| Dual Optima Red Tops: 2000 Cold Craking Amps | Denali Projectors |

  18. #18
    Registered User
    Join Date
    Jul 2010
    Location
    Lehigh Valley, PA
    Posts
    63

    Re: 4L80E, TC lockup erratic

    i have oil leakin into my cyl 8 from when the dealer replaced my intake gasket. i made them do it which was a mistake cuz i only had the truck a week before it went. they stuck a ground wire into my valve cover in cyl 8 but nothin on the wire showed any kind of damage done to anything. changed the valve cover gasket but i still have a leak into cyl 8. it completely fouls out the plug. looks like the tip of a marker and not a spark plug at all. the electrode and everything gets covered in what looks like burnt oil. im gonna pull that plug and see if its messed up again. also, when i put the truck in gear ( drive trhu 1st and reverse) ... i have a loud whining almost like a whistling noise like i have air leaking out somewhere. not sure what thats all about but its been doin that since i had the truck. gets louder when its hot.

    -2500ak : i tried to send you a message but your quota for messages is full.
    Last edited by 2000crewcabOBS; 08-05-2010 at 07:03 PM.

  19. #19
    Registered User 2500ak's Avatar
    Join Date
    May 2007
    Location
    Alaska
    Age
    25
    Posts
    2,525

    Re: 4L80E, TC lockup erratic

    Quote Originally Posted by 2000crewcabOBS View Post
    i have oil leakin into my cyl 8 from when the dealer replaced my intake gasket. i made them do it which was a mistake cuz i only had the truck a week before it went. they stuck a ground wire into my valve cover in cyl 8 but nothin on the wire showed any kind of damage done to anything. changed the valve cover gasket but i still have a leak into cyl 8. it completely fouls out the plug. looks like the tip of a marker and not a spark plug at all. the electrode and everything gets covered in what looks like burnt oil. im gonna pull that plug and see if its messed up again. also, when i put the truck in gear ( drive trhu 1st and reverse) ... i have a loud whining almost like a whistling noise like i have air leaking out somewhere. not sure what thats all about but its been doin that since i had the truck. gets louder when its hot.

    -2500ak : i tried to send you a message but your quota for messages is full.
    Whining could be the torque converter, I know that some aftermarket ones have a tendency to do that. Perhaps you were on track with the drainback issue. If you have a cylinder that isn't firing regularly then that's probably the cause of its reluctance to lock-up.
    Last edited by 2500ak; 08-06-2010 at 06:49 PM.

    Transgo HD2 | Magnaflow DI/DO | CAI | BlackBear Tune| Dual Optima Red Tops: 2000 Cold Craking Amps | Denali Projectors |

  20. #20
    Registered User
    Join Date
    Jul 2010
    Location
    Lehigh Valley, PA
    Posts
    63

    Re: 4L80E, TC lockup erratic

    the plug was really messed up when i pulled it today. i cleaned it and stuck it back in fired it up and ran it. misfire went away and trans seemed fine although i did not drive it very far. the only way i can think of that oil can get onto the plug would but thru the valve seal... line locked the truck in the driveway and tires wanted to spin at about 2000k. i can feel it start to lock at about 1600. not sure if the obs has the torque management bs in the newer style trucks or not.

 

 
Page 1 of 2 12 LastLast

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •