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Thread: 4L60E Misbehaving on the highway - Drivability

  1. #1
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    4L60E Misbehaving on the highway - Drivability

    First time using the HP Tuner and have done some homework so will try to explain what is happening and what I know.

    Trans is rebuilt and all parts have been checked out by two transmission shops. Both say the trans is doing what it is commanded, when it is commanded and no code or issues are noted.

    When on the highway the TC drops out of lockup at the slightest downhill at 70 MPH. I have put my cheapo reader on it and the TPS is reading about 20% when it drops out of lockup and then locks back up at about 25%. That causes a lot of lock and unlock cycles on a long trip and is just not normal.

    I pulled my TCC Apply/Release tables and I don't see anything that says it should be commanding that way

    HPTTCC1.PNG

    As I understand it, this says that the 4th Apply at highway speeds should lock up the TC between 53 and 59MPH for any throttle position under 43.8 percent and once I hit 75 it should stay locked at any TP under 50%. The unlock throttle positions are up in the 70 - 80% ranges.

    Any ideas why this might be happening? I will go take a drive and see if I can log when it happens.

    Parts replaced and cleaned///
    New TPS
    New MAF
    Cleaned Throttle Body
    New TCC Solenoid and harness
    New Torque converter and valve body (OE spec replacements from TransStar)
    Trans is mildly built, z pack clutches, hardened shells, wide band, larger boost valve, PWM not blocked

    Thanks in advance, have a long trip planned and was hoping to square this away this week but this was unexpected.
    Last edited by swearingencj; 1 Week Ago at 11:40 PM.

  2. #2
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    I went out and drove it and logged the drive. I am attaching the tune and the log from the drive. A few minutes into the drive once I hit 70 you'll see the RPM jumping from ~2000 to ~3000. TCC says it is still locked but it is slipping. It only does this at part throttle (about 20% on the TPS) and then stops slipping at around 25%. During this drive, I am on the highway and every time it slips I am headed down very small hills. It happens with or without cruise control, meaning I can reproduce this with my foot on the accelerator and cruise not engaged.

    Hoping someone can give me some insight.

    Log from my drive
    031824StockTune.hpl

    Downloaded Tune (fresh GM Flash from the dealer)
    2000BurbOrig.hpt

  3. #3
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    Look at ECM 5682 and 5683

    Give this one a try and datalog all the TCC channels. It will tell you why its being unlocked.
    Attached Files Attached Files

  4. #4
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    Thanks RDF1,

    Thanks, couple of clarifications and I can run this after work. When the TCC slips in that log file, it is still commanded as locked and shows locked with a TCC Slip of 115%. I looked at a compare of my original file and this one and looks like the change is zeroing out the Lo Speed TPS Lo and High settings, are those the only changes? Also I don't see ECM 5682 and 5683 in my list of channels, it skips from 4401 to 6601. What are those Channels, not sure why I don't have them. This is on a 2000 Suburban.

    I was thinking that with the changes to the internals and a higher pressure boost valve, should my max pressure be increased? Or possibly the PWM Duty Cycle maxed out at highway speeds bringing more pressure to the TC?

  5. #5
    Senior Tuner TheMechanic's Avatar
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    Ctrl+n 5682

  6. #6
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    Torque converter lockup on 99-00 trucks are notoriously bad about locking promptly and staying locked. There was talk a while back of a maximum slip allowable between locked and not locked that was responsible.

    I've flashed 01-02 operating systems in and completely fixed it.


    There is also a fuse on most GM's that applies power to the PCM while NOT on the brake. If this fuse is bad the TCC will release at the slightest lift of the gas pedal. The fuse is sometimes labeld TCC brake. I'd look at your schematics to know which for sure. But it is HOT while NOT on brake. Opposite of what you would think.
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  7. #7
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    Thanks Alvin,

    I checked all of my fuses and only have one related to brakes and none with TCC in the name. The brake fuse was good. On this model, I believe the brake switch itself has a lead that signals the transmission when brake is applied, not sure where that goes, I need to trace that.

    Do you have a clean 01-02 file I can look at to compare the diffs with my current file?

  8. #8
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    Searched in the add channel window and there is nothing there, did the keystroke above and nothing happened. What are 5682 and 83 called?

  9. #9
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    Tested TCC PWM Lock/Unlock

    Thanks for the replies so far, it's given me some things to work out and a few more ideas.

    Tonight I drove it with the following manually commanded on

    hpttcc2.PNG

    While I had the TCC PWM Lock/Unlock toggled Green on the On button the trans acted completely normal. No weird behavior on the highway at all, trans locked up cruising at 70 and no big slip going down hill.

    I toggled the on button off (but not the Off button on), both grey and ran it down some hills and it went back to the bad behavior. If I toggled the on button while the trans was slipping on a down hill, it immediately stopped slipping.

    Unfortunately, my laptop died on the way home and I lost the logfile.

    Now the question, what does this mean? Can I/Should I tune it to run this way all of the time? Shouldn't it already run this way? Honestly, the trans felt freer and smoother throughout the whole drive with that toggled on.
    Last edited by swearingencj; 1 Week Ago at 09:28 PM.

  10. #10
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    Tonight I flashed several test files including RDF1's file, none changed anything much. I maxed out the Duty Cycles to 100/900, made major adjustments to the Apply/Release Tables. Did these all individually and then combined them all in one file. At the end of the night I went back to the original. The only thing that makes any difference is commanding on the TCC PWM Lock/Unlock or the TCC Solenoid. Clearly those two thing just force lock the TC and won't allow any slip.

    Anyone have any ideas what would command the TC to slip under very predictable conditions? Like I said, it happens on the highway on cruise control or I can make it happen with my foot on the accelerator by lifting to a throttle position of 20%.

    Frustrating. I am driving cross country on Friday morning and actually considering plugging in and toggling the TCC while I am on the highway.

    I called my mechanic tonight and thinking about replacing the TCC PWM Solenoid which appears to be different from the TCC solenoid that is wired to the harness (already replaced).
    Last edited by swearingencj; 1 Week Ago at 09:40 PM.

  11. #11
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    I am coming in late on this one, I might able to help but I would need a log with all the relevant PIDs to be able to help. If you can take another one and use the following channel config file it would be great. 4L60E.Channels.xml
    Robert Moreau
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  12. #12
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    Quote Originally Posted by TransGo Robert View Post
    I am coming in late on this one, I might able to help but I would need a log with all the relevant PIDs to be able to help. If you can take another one and use the following channel config file it would be great. 4L60E.Channels.xml
    Thanks Robert,

    Here are three files.

    The new tune, standard GM tune with one adjustment for tiresize. Very minor
    Next file (032124731.hpl), highway drive. Each time you see the RPM climb from about 2k to about 2.8k i am going down hill in cruise control. Happens if I don't use cruise and lift my foot a bit on the pedal
    Last file (032124731tccpwm.hpl) hilly drive but toggled the TCC PWM on

    2000BurbOrig26570R16.hpt
    032124731.hpl
    032124731tccpwm.hpl

    I really appreciate you looking at this for me

  13. #13
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    Quote Originally Posted by swearingencj View Post
    Thanks Robert,

    Here are three files.

    The new tune, standard GM tune with one adjustment for tiresize. Very minor
    Next file (032124731.hpl), highway drive. Each time you see the RPM climb from about 2k to about 2.8k i am going down hill in cruise control. Happens if I don't use cruise and lift my foot a bit on the pedal
    Last file (032124731tccpwm.hpl) hilly drive but toggled the TCC PWM on

    2000BurbOrig26570R16.hpt
    032124731.hpl
    032124731tccpwm.hpl

    I really appreciate you looking at this for me
    Ok it is not a command issue, this is an internal issue. From the looks of it it seems you don't have enough AFL pressure when you are under light throttle. It is not the lock-up that is slipping, it is going back to third gear as you can see in the screenshot below, the engine RPM and output RPM are the same 1 to 1 ratio therefore it is going to third gear. Since there is no input speed sensor in those earlier ones, the computer register it as if it was a TCC slip but it is not. YOu can also see that the lock-up command remains steady. Anyways, it is a valve body issue most likely, it should be easy to fix with our oversized valve. https://transgo.com/product-details/...ize-afl-valve/
    4-3.png
    Robert Moreau
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    2621 Merced Avenue El Monte, CA 91733 USA
    Calibration | Innovation |Performance
    https://transgo.com/our-products/

  14. #14
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    Quote Originally Posted by TransGo Robert View Post
    Ok it is not a command issue, this is an internal issue. From the looks of it it seems you don't have enough AFL pressure when you are under light throttle. It is not the lock-up that is slipping, it is going back to third gear as you can see in the screenshot below, the engine RPM and output RPM are the same 1 to 1 ratio therefore it is going to third gear. Since there is no input speed sensor in those earlier ones, the computer register it as if it was a TCC slip but it is not. YOu can also see that the lock-up command remains steady. Anyways, it is a valve body issue most likely, it should be easy to fix with our oversized valve. https://transgo.com/product-details/...ize-afl-valve/
    4-3.png
    This is a new Valve Body, bought from TranStar in Jun 2023. Is is possible the TCC PWM Solenoid is defective when not fully engaged?

    In that screen shot, it shows the current Trans Gear as 4. Why would it log 4th gear if it is in 3rd?
    Last edited by swearingencj; 6 Days Ago at 08:30 PM.

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    Quote Originally Posted by swearingencj View Post
    This is a new Valve Body, bought from TranStar in Jun 2023. Is is possible the TCC PWM Solenoid is defective when not fully engaged?

    In that screen shot, it shows the current Trans Gear as 4. Why would it log 4th gear if it is in 3rd?
    New just means Neve Ever Worked, you are the first one to test it. The TCC PWM solenoid has nothing to do with this, it is strictly a solenoid, feed orifice, or AFL issue.
    Robert Moreau
    Technical Sales and Marketing Support Specialist
    TransGo
    2621 Merced Avenue El Monte, CA 91733 USA
    Calibration | Innovation |Performance
    https://transgo.com/our-products/

  16. #16
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    Quote Originally Posted by TransGo Robert View Post
    New just means Neve Ever Worked, you are the first one to test it. The TCC PWM solenoid has nothing to do with this, it is strictly a solenoid, feed orifice, or AFL issue.
    lol, I guess that's fair, I certainly don't know where that valve body came from but I'm sure I can cash in the warranty.

    One other question, When I command the TCC PWM "on" from here

    hpttcc2.PNG

    The slipping stops immediately. Would that narrow any of the possibilities?

  17. #17
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    I would need to see a log of that with the same PIDs selected to know why it is different. It might command the pressure control solenoid differently.
    Robert Moreau
    Technical Sales and Marketing Support Specialist
    TransGo
    2621 Merced Avenue El Monte, CA 91733 USA
    Calibration | Innovation |Performance
    https://transgo.com/our-products/

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    its the other file labeled tccpwm.

    Thanks for sticking with me

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    Quote Originally Posted by swearingencj View Post
    its the other file labeled tccpwm.

    Thanks for sticking with me
    Ok I guess I will have to get off my but and back in the computer to look at it. When I briefly looked at it earlier the data for the TCC PWM solenoid was really odd , for a good part of the movie it kept in cycling up and down. I figured it must have just been a corrupted file.
    Robert Moreau
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    Calibration | Innovation |Performance
    https://transgo.com/our-products/

  20. #20
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    Quote Originally Posted by swearingencj View Post
    its the other file labeled tccpwm.

    Thanks for sticking with me
    I went back and looked at it and it never even goes in lock-up once in that log, so the pump RPM never went low enough under light load to cause the unit to downshift from 4th to 3rd.
    Robert Moreau
    Technical Sales and Marketing Support Specialist
    TransGo
    2621 Merced Avenue El Monte, CA 91733 USA
    Calibration | Innovation |Performance
    https://transgo.com/our-products/