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Thread: Built 6l80 failed, help me diagnose why!

  1. #1
    Tuner in Training
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    Jul 2019
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    Built 6l80 failed, help me diagnose why!

    I will try to put all the useful info in here to start. The car is a 2009 G8 with a LSA blower. The car makes an estimated 650-680whp. I put approximately 14k miles on the bone stock 6l80 with 600whp and had no issues. (92k-106k) I overrevved the stock block and tweaked a rod so while the motor was being built, I built the transmission.

    Parts List:
    New bellhousing/pump, upgraded pump rotor, all the Sonnax upgrades
    New 1-2-3-4, 3-5-r assembly, Sonnax 1-2-3-4 piston, Sonnax 4-5-6 piston kit
    Sonnax billet intermediate shaft for factory clutch pack
    Alto Red power-pak in 3-5-r, 4-5-6, and 2-6. Raybestos stage 1 in 1-2-3-4. No wave plate in 2-6 and 4-5-6.
    Sonnax zip kit and tchm seal kit.
    New GM ZL1 converter, camaro pan, ctsv filter, Hayden 11x11 cooler inline with factory radiatior.

    At almost 3k miles on the built motor/transmission, I made a 3-4 and into 5th pull. Everything felt good during the pull, shifts felt fine. It shifted to 6th and was normal. I went to pull off around a turn and it locked in 4th and threw a CEL. I got it home and it was showing P0700 and P0797. Attempted to reflash the trans, didn't work. Revving in park would push the car forward (I was logging here and temps got up to 190). I lost all gears and had it towed to a local transmission shop. They pulled it apart and found every clutch pack burned up. They couldn't find any issues with the rebuild, everything was in spec and pump looks good. They believe the tchm failed and caused pressures to get screwed up and toast the clutch packs. No metal in the pan indicating torque converter failure, only clutch material.

    The transmission never ran hot, it would sit in the 140-150 range. I never experienced slip and things that would indicate something was wrong. The only thing I had happen worth mentioning was at about 1500 miles, I started hearing what sounded like loose flexplate bolts or cracked flexplate at 1800 rpm only. I checked everything, could never find the source of the noise. It was only at 1800rpm, revving up or down.

    I'm having a new GM 6l80 put in and I'll bring my transmission back to check closely and rebuild as a spare. But I'd like to see what the experienced guys think of my tune. It was completely self-tuned after doing a bunch of research and reading on 6l80 tuning. I just want to verify the tune wasn't the cause or part of the reason for the failure.


    If you don't want to read all that, I'm looking for opinions on my tune to make sure it wasn't the reason for failure.

    TIA!
    Attached Files Attached Files
    09 G8 GT - Forged L76 6.0 - K1 crank, K1 H-beams, Diamond pistons, BTR PDS 3, BTR .660 kit, stock LSA w/ZL1 re-enforced lid, 2.45 upper, 4" intake w/ LS7 MAF, Kooks 1 7/8" long tubes, Kooks 3" x pipe, Corsa axleback, ID1050x w/ ZR1 rail, CTSV V2 pump, Vaporworx PWM controller, Circle D Lvl 3 6l80 w/ FTI triple disc

    Engine assembled by Nickens Brothers, everything else built, assembled and tuned by me.

  2. #2
    Advanced Tuner
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    Nov 2006
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    609
    Have you diagnosed the P0797? Looks like a solenoid failed by the code.
    Tuner at PCMofnc.com
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  3. #3
    Tuner in Training
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    Jul 2019
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    Quote Originally Posted by Alvin View Post
    Have you diagnosed the P0797? Looks like a solenoid failed by the code.
    Right, the solenoid is locked "on" which I believe makes the 4-5-6 stay engaged. Which is why we think the tchm failed (or solenoid inside). I just wanted to see if my tune looks ok or if I did something that played into the failure.
    09 G8 GT - Forged L76 6.0 - K1 crank, K1 H-beams, Diamond pistons, BTR PDS 3, BTR .660 kit, stock LSA w/ZL1 re-enforced lid, 2.45 upper, 4" intake w/ LS7 MAF, Kooks 1 7/8" long tubes, Kooks 3" x pipe, Corsa axleback, ID1050x w/ ZR1 rail, CTSV V2 pump, Vaporworx PWM controller, Circle D Lvl 3 6l80 w/ FTI triple disc

    Engine assembled by Nickens Brothers, everything else built, assembled and tuned by me.

  4. #4
    Tuner in Training
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    To update this, the transmission from GM would not program (at least the guy the shop uses couldn't get it to). So I'm now building a Circle D level 3 kit with my core. Pulling it apart, I haven't found any issues aside from clutch material all over. The sprag top plate was bowed outward, allowing up and down play but it still locked up with no issues and doesn't appear to have abnormal wear. I didn't pay attention to how I had the snap ring positioned when I pulled it apart, I may have aligned it incorrectly. Although I took my time when building it and used the manual step by step.

    There was a decent amount of clutch material in the techm filter and solenoid films. The valve body wasn't too dirty, the valves looked fine as well. I had a couple bushings that were worn so those have been replaced. Still not finding any glaring reason it failed other than the techm and possibly my tune for the transmission failing.


    No one has any input on the tune posted here? I didn't think it was overly aggressive, I've seen a number of tunes running way more pressure and TM totally disabled. I will probably go with a professional 6l80/90 tuner either way as I don't want to risk another rebuild.


    Side note, the Circle D kit seems pretty solid. Only thing I didn't spring for was a billet planetary. I'll be running the powerglide 4-5-6 clutch pack this time around which seems like a massive upgrade on paper at least.
    09 G8 GT - Forged L76 6.0 - K1 crank, K1 H-beams, Diamond pistons, BTR PDS 3, BTR .660 kit, stock LSA w/ZL1 re-enforced lid, 2.45 upper, 4" intake w/ LS7 MAF, Kooks 1 7/8" long tubes, Kooks 3" x pipe, Corsa axleback, ID1050x w/ ZR1 rail, CTSV V2 pump, Vaporworx PWM controller, Circle D Lvl 3 6l80 w/ FTI triple disc

    Engine assembled by Nickens Brothers, everything else built, assembled and tuned by me.

  5. #5
    Advanced Tuner
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    Apr 2016
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    Cal is allowing TCC operation at WOT. I wouldn't do that with a stock converter.

    Also, the TCC Regulator Offset may need to be raised some. I had to bump mine up considerably to prevent tcc slip when engaged, even at cruise throttle, and even with Desired slip zeroed out. In addition, decreasing the throttle % setting so that it releases sooner when crowding the throttle is a good idea. I did so after I added a blower. Reason being, you are making considerably more torque with the blower at, say 25% throttle or wherever, than when the motor was stock. It is really a matter of test driving/logging tcc slip vs tps to see where you need to balance an increase in the Offset vs just disengaging the TCC all together above a certain throttle. You don't want to go higher than necessary with the Offset, as I have heard the stock converters can also suffer from hard part fractures as well. Zeroing the TCC Desired Slip is not the end-all without the above changes if you want to prevent it from slipping.

  6. #6
    Tuner in Training
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    Quote Originally Posted by NotSure View Post
    Cal is allowing TCC operation at WOT. I wouldn't do that with a stock converter.

    Also, the TCC Regulator Offset may need to be raised some. I had to bump mine up considerably to prevent tcc slip when engaged, even at cruise throttle, and even with Desired slip zeroed out. In addition, decreasing the throttle % setting so that it releases sooner when crowding the throttle is a good idea. I did so after I added a blower. Reason being, you are making considerably more torque with the blower at, say 25% throttle or wherever, than when the motor was stock. It is really a matter of test driving/logging tcc slip vs tps to see where you need to balance an increase in the Offset vs just disengaging the TCC all together above a certain throttle. You don't want to go higher than necessary with the Offset, as I have heard the stock converters can also suffer from hard part fractures as well. Zeroing the TCC Desired Slip is not the end-all without the above changes if you want to prevent it from slipping.
    Thanks for the input! I struggled finding real information about what, how and why TCC stuff needs to be tuned. I've also seen some info stating the virtual torque table needs to be adjusted but no real explanation on how to do so correctly. I've also heard that injector scaling has an effect on the virtual torque tables.
    09 G8 GT - Forged L76 6.0 - K1 crank, K1 H-beams, Diamond pistons, BTR PDS 3, BTR .660 kit, stock LSA w/ZL1 re-enforced lid, 2.45 upper, 4" intake w/ LS7 MAF, Kooks 1 7/8" long tubes, Kooks 3" x pipe, Corsa axleback, ID1050x w/ ZR1 rail, CTSV V2 pump, Vaporworx PWM controller, Circle D Lvl 3 6l80 w/ FTI triple disc

    Engine assembled by Nickens Brothers, everything else built, assembled and tuned by me.