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Thread: 8l90e swap

  1. #1
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    8l90e swap

    Ok,
    I have a 2016 camaro lt1/8l90e swapped in a 66 chevelle. Motor runs fine, trans shifts and out of gear fine, but, when in drive and take off it feels like I am a higher gear and throttle will only go to 30%.
    I have tried to do a fast learn on the trans but unable to saying that it has dtc. Only codes in the trans are u0140 no com with bcm and u0121 no com with ebcm.
    when with koeo tps does not go over 38% as accel pedal reads 99.6%
    I also don't understand why some codes I have tuned off in the ecm emissions codes they are still present when I scan for codes but won't bring the ses light on.
    Thanks

  2. #2
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    You won't get much help without a log and a calibration file.

    Permanent DTCs will not clear until they have passed even if you have turned them off.

    What harness are you using?

  3. #3
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    Modified factory harness. Ecm, tcm, and ccm.
    Attached Files Attached Files
    Last edited by bonesv8; 10-11-2021 at 04:05 PM.

  4. #4
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    Is a bcm required?

  5. #5
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    What rearend ratio do you have in the car? The current gear shifts way too soon if thats right. I know the 8 and 10 speeds don't like crazy gear ratios and don't shift right.

  6. #6
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    Looks like you are defaulted in 3rd gear.

    You may need to fix some of those DTCs that set permanent before you can do a fast adapt, I didn't dive into which ones were which but it could be an ECM DTC preventing the fast learn.

    Your PRNDL status is unknown, unsure if this could be an issue but that did jump out at me.

    What are you using for a brake pedal switch?

  7. #7
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    Quote Originally Posted by K-fed View Post
    What rearend ratio do you have in the car? The current gear shifts way too soon if thats right. I know the 8 and 10 speeds don't like crazy gear ratios and don't shift right.
    The car has 3.08. The log was the first drive on the road. It doesn't feel like it shifts...it feels like it's stuck in a higher gear like 3rd. It's a dog off the line.

  8. #8
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    Cadillactech:
    I did notice the unknown also...not really sure what that means. I tried moving the shift cable around thinking It was out of adjustment but no dice. It does feel like it's stuck in 3rd.
    I was thinking about the ecm dtcs... Evap vent and purge codes, eco mode switch code, bpp sensor code. No com with ebcm and bcm.
    I am running a 12v wire off the brake switch to the ecm. I do get applied and released in the scanner for the brake pedal.

  9. #9
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    Actually the more I drive it, the trans is stuck in 3rd gear. watching the gear ratios once I start moving it stays at 2.08:1 which is 3rd gear.

  10. #10
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    I just noticed in your log you have 2 current trans gear that read different. One looks like its shifting but way fast for the speed. The other in 3rd gear like you said. Like Cadillactech said the PRNDL are unknown which could be the issue. Are you able to force the transmission to shift through the controls in the scanner?
    Last edited by K-fed; 10-16-2021 at 11:47 AM.

  11. #11
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    I saw that too. with the snap on scanner hooked up it reads correct...no unknown 82.
    forcing the trans to shift does nothing with the hptuner or the snap on scanner.
    The other day I dropped the pan after I ohmed out all the wires from the trans to tcm and rechecking all my power and grounds are current and in the proper location. Inside the trans looks fine and I can operate the all the solenoids with the scanner.
    So I am unsure whats going on. No codes driving around the block besides no comm with ebcm or bcm.
    Drove the car little more today data logging. watching the pcs comd pressures for 1-5, they change in reverse and change in drive but that's it. the command pressures don't change like the tcm is not commanding other gears.
    I am missing something, just can't figure it out.
    Last edited by bonesv8; 10-18-2021 at 02:43 PM.

  12. #12
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    Any updates on this? Shouldn't the codes for u0140 no com with bcm and u0121 for ebcm be set to "no error reported" since you don't have them anymore? The same goes for your rear O2's, evap, etc...

  13. #13
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    I had a similar but reverse problem in my Chev L83/8L90 Jeep. I saw the gear ratio set at 3.42 and thought hell I have 4.10 gears. Set it to that and it would kick down at 60mph to some ungodly gear and scream. Changed it back and all good again. Tuner told me that is how they react. Try setting the ratio down to something like (can't remember exact number) 2.43 and go for a drive as it should create my problem in reverse order. Don't go far as you might have to go back and change it. Also do you know that the throttle pedal for the 6L80/90 is not the same as the 8L90/10L90 units. Different part number. Just mentioned that because it relates to the transmission more than the engine which is the same basically.
    Last edited by JKLTGuy; 3 Weeks Ago at 10:27 PM.

  14. #14
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    Try this. Sometimes the brake pedal position codes will cause trans limp mode.
    Attached Files Attached Files

  15. #15
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    UPDATE!! Thank you K-fed and sevinn. I was unaware that under the error mode column there was a drop down menu per code. So I set "no error reported" to all the necessary codes and the car rips, burn outs for distance lol.
    JKLTguy the car has 3:08 gears in prep for this build.

  16. #16
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    Quote Originally Posted by bonesv8 View Post
    UPDATE!! Thank you K-fed and sevinn. I was unaware that under the error mode column there was a drop down menu per code. So I set "no error reported" to all the necessary codes and the car rips, burn outs for distance lol.
    JKLTguy the car has 3:08 gears in prep for this build.
    That's great to hear. Thanks for the update!