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Thread: 4L60E Shifting Way too Early

  1. #1
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    4L60E Shifting Way too Early

    So I finally got the Gen 3 LM7 w/ 4L60E in my '66 C10 tuned and running quite nicely. The problem now is that it's shifting way too early - I have the speedometer / VSS properly calibrated to my gear ratio / tire size, but when driving, it feels like it's bogging down HARD especially at lower gears, and not accelerating properly, so I plugged it into the VCM Scanner so I can see what's going on.

    From what I can tell, it is shifting gears, but not at the right speeds. I can physically feel the 1-2 shift happening at close to 5 MPH. And earlier today I was in 4th gear going 25 MPH.

    Any idea on where I should look first to fix this?

  2. #2
    Tuning Addict blindsquirrel's Avatar
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    Quote Originally Posted by spectre1995 View Post
    Any idea on where I should look first to fix this?
    screenshot.17-10-2021 13.31.17.png

  3. #3
    Advanced Tuner dhoagland's Avatar
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    screenshot.17-10-2021 13.31.17 (1).png

    Request permission to use photo in the future
    2011 Camaro 2SS Convertible L99 Bone Stock for now
    2003 Dodge 2500 5.9 Cummins QC 4x4. Airaid, 2nd Gen Intake, Grid Heater Delete, D-Tech 62/65/12, Magnaflow. Bully Dog: Propane Injection, Triple Dog W/Outlook Crazy Larry. Edge EZ, BD Flow-Max, 48RE: Sonnax Sure Cure/Transgo combination, Derale turbulator, billet input, Triple Disc, Super servo, 4 ring Accumulator. :beer

  4. #4
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    Just double checking - presumably you're looking for an upload of the tune file I'm using?

  5. #5
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    Tune and log usually.

  6. #6
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    I'll have to read up on how to compile a log - I've just been watching the live readouts

  7. #7
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    For starters, here's the tune file. I don't currently have a log but I'll get one later today.
    Attached Files Attached Files

  8. #8
    Advanced Tuner dhoagland's Avatar
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    From your scanner when you click the stop scanning Icon...

    You will be looking at a screen like the picture.
    Then you can click log file, the save log file as from the drop down. Or Click the "Save as" File icon.
    Then save to a folder of your choice. I believe the default is something like this C:\Users\daniel.hoagland\Documents\HP Tuners\VCM Scanner\Logs\Jesse

    After Saved you can follow blindsquirrel's upload guide
    Log File.JPG
    2011 Camaro 2SS Convertible L99 Bone Stock for now
    2003 Dodge 2500 5.9 Cummins QC 4x4. Airaid, 2nd Gen Intake, Grid Heater Delete, D-Tech 62/65/12, Magnaflow. Bully Dog: Propane Injection, Triple Dog W/Outlook Crazy Larry. Edge EZ, BD Flow-Max, 48RE: Sonnax Sure Cure/Transgo combination, Derale turbulator, billet input, Triple Disc, Super servo, 4 ring Accumulator. :beer

  9. #9
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    And here's the log from a quick lap around the block
    Attached Files Attached Files

  10. #10
    Tuning Addict blindsquirrel's Avatar
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    Well that's definitely weird all right. Also the 1st-3rd-1st every time you come to a stop.

    Was the file's rear gear originally 3.73, or did you change that and then scale the shift points? If you did change it, have you tested with everything (even speedo) reverted to stock, just to see if it affects this specific problem?

  11. #11
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    Yeah I think it was originally 3.43, I had tested it with that and had a similar issue. I changed it to 3.73 to match what's in the truck's rear end and it doesn't seem to have changed much, at least not enough for me to notice anything significant. Before changing it, the speedo was wildly inaccurate - now it's "close" but not 100% perfect.

  12. #12
    Tuning Addict blindsquirrel's Avatar
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    I wouldn't worry about the accuracy of the speedo until it's shifting at the correct MPH (indicated, not actual). If it shifts when it should with everything copied from a stock file you can put your changes back in one at a time.

    I see the PCM's VIN is a 2WD, is it still? You haven't changed anything in the trans like output shaft? Did the engine/trans/PCM all come from the same donor?

  13. #13
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    Yea it's still a 2WD. The engine and trans came from the same vehicle (2004 / 2005 ish Chevy Tahoe 5.3L non flex w/ 4L60E) but the PCM came from another vehicle (2005 Chevy Express 6.0L with 4L60E).

    I didn't change much from the stock file other than removing some evaporative / emissions related things from the DTC list. I think I made some other small changes as well, but nothing to the transmission with the exception of the gear ratio / tire size calculator. Also when I ran the stock file with no modifications to it about a month or so ago, I had the same shifting issues

  14. #14
    Tuning Addict blindsquirrel's Avatar
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    Are you sure the '05 Express PCM service number is compatible with the '04 Silverado file you put on it?

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    As far as I've been told, they're compatible but I'm very new to all of this so I have no way of really knowing until I try it out. Have you found anything that might indicate this might be the issue? Or possibly anything in the tune file that could be a potential factor?

  16. #16
    Tuning Addict blindsquirrel's Avatar
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    What was the VIN of the '05 Express? When you go look up a PCM for that VIN, does that number also interchange with the new file? From what I'm seeing, without a VIN to go on, they use different service numbers ('04 Silverado 1500 LM7 and '05 Express 2500 LQ4). If they were functionally identical and could run the same calibrations the parts listings would normally get consolidated down into a single (or the minimum number) of part numbers.

  17. #17
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  18. #18
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    From the tune that was on the PCM before I flashed it;

    Creation Date: 6/28/2022 12:39:45 AM

    VIN: 1GBJG31U151196734
    2005 Chevrolet Express 3500, 6.0 L, V8

    Hardware: P59, GM Gen3 V8, 4.3L V6
    VIN: 1GBJG31U151196734
    Serial: 0MA05QGV5025
    OS: 12592618


    From the tune I flashed on it (from the repository);

    Creation Date: 6/22/2016 7:48:24 PM

    VIN: 2GCEC19T141186089
    2004 Chevrolet Silverado 1500, 5.3 L, V8

    Hardware: P59, GM Gen3 V8, 4.3L V6
    VIN: 2GCEC19T141186089
    Serial: 1LA08U7Y3265
    OS: 12587603
    Last edited by spectre1995; 07-19-2022 at 08:42 PM.

  19. #19
    Tuning Addict blindsquirrel's Avatar
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    04 Silverado 2GCEC19T141186089: 12581565, 89017733
    05 Express 1GBJG31U151196734: 89017749, 12589462, 12602801

  20. #20
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    Got it - so it's a PCM issue after all?

    Should I just source one from a junkyard or order it new?