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Thread: converter will not lock under wot

  1. #1
    Senior Member camcojb's Avatar
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    Default converter will not lock under wot

    it definitely locks, and is fine at anything under 100% tp. But at wot if it down shifts it unlocks and will not lock again.

    I can get it to work properly for 1-3 times if I reload a different tcm tune, or usually if I just reload the same tune. But it always goes back to not locking. If I get it locked, and then go wot at a speed that doesn't allow downshifting, then it will remain locked throughout the run. But if it's completely locked in say 5th gear at 50 mph or so and I go wot, it downshifts and will not re-lock at any speed.

    I've tried everything I can think of. I've lowered the locking to super low mph's also, but no matter what, if it downshifts it's over. Like I said it will work fine a time or two or three after a flash, just long enough for me to think it's fixed, but then you jump in the truck the next time and no lock. Does it in normal and tow/haul.

    Again, this is only at wot, no problems locking at lower tp%. I've reset taps and it's hit or miss as to whether it will work or not. This is on a high power tune with twins, SCIV and 1058 billet converter, LMM with 6 speed.

    Final question since I know Mike L will ask, but is there any way to know if the tcc is being commanded in the EFI Live software? I saw a pid but it does not work as far as I can tell. I do not have access to a Tech II. I do not think there's any issues with the trans or converter, they work perfect except for this one glitch. It never fails to lock at normal or spirited driving. It's like once you get above a certain power level there's a table in the tcm that says "hell no, not going to lock it............. " I've heard this is an issue on high powered trucks, but as of yet I have not heard of anyone solving it.



    Jody
    07.5 4X CC 2500HD, EFI Live, MBRP exhaust
    new updated website!

  2. #2
    Lifetime Member vortecfcar's Avatar
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    Jody,

    I have a log file sitting in my email box from a customer with an issue I fear is similar to yours. I have a quick question for you just so that we're on the same page.

    Have you tried raising your minimum TCC apply?

    My thought is that the Alllison has a table that references TCC slip to PWM gain in order to figure out how much pressure it should apply to the converter clutch in order to get a clean, but not harsh lock. If you downshift under WOT you may put the TCC slip axis beyond the factory limits or into a new range where lockup is simply abandoned. My first plan of attack on this truck was going to be to raise minimum lockup pressure to see if we can get the converter to lock quickly before it goes into the dead zone. Second would be to see if there's a way we can aviod converter unlock on certain shifts altoghether.

    I still have to look over the logs when I get to my other computer.

    Nick

  3. #3
    Senior Member camcojb's Avatar
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    Quote Originally Posted by vortecfcar View Post
    Jody,

    I have a log file sitting in my email box from a customer with an issue I fear is similar to yours. I have a few questions for you just so that we're on the same page.

    Have you tried raising your minimum TCC apply?

    My thought is that the Alllison has a table that references TCC slip to PWM gain in order to figure out how much pressure it should apply to the converter clutch in order to get a clean, but not harsh lock. If you downshift under WOT you may put the TCC slip axis beyond the factory limits or into a new range where lockup is simply abandoned. My first plan of attack on this truck was going to be to raise minimum lockup pressure to see if we can get the converter to lock quickly before it goes into the dead zone. Second would be to see if there's a way we can aviod converter unlock on certain shifts altoghether.

    I still have to look over the logs when I get to my other computer.

    Nick

    no, raised the maximum which I thought helped, but after 3 wot datalogs it wasn't locking anymore.
    What you're thinking would go exactly with what is happening. I'll give it a shot and see what happens. My stock tune was zeroed out on the minimum table everywhere.

    The only way I've been able to keep it locked every time at wot is to not let it downshift, which is easy to do. However, that's certainly not an ideal trans tune on the street.

    Thanks Nick, I'll post back.

    Jody
    07.5 4X CC 2500HD, EFI Live, MBRP exhaust
    new updated website!

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    Junior Member OSUBeaver's Avatar
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    How about when you do a boosted 4wd launch from a dead stop?

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    Senior Member camcojb's Avatar
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    Quote Originally Posted by OSUBeaver View Post
    How about when you do a boosted 4wd launch from a dead stop?
    nope, same issue. It will lock sometimes a run or two after flashing the tcm tune in, but then stops locking altogether.

    Jody
    07.5 4X CC 2500HD, EFI Live, MBRP exhaust
    new updated website!

  6. #6
    Junior Member OSUBeaver's Avatar
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    Not meant to be a dumb question, but do you mean "stops locking" like won't lock at any speed RPM, etc..... or just locks late?

    Or does it just spin like a mother from a stop like mine......... I hit 3500rpm on the 1-2 shift, 3700 right before it locks, then it shifts into 3rd and we're off to the races.

    Copilot doesn't do poop..... race mode or not.

  7. #7
    Lifetime Member IdahoRob's Avatar
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    This is a problem for some trucks, and not just the LMM's I have a customer with a 700-800HP LB7 that is having the same issue.

    The TCM does see too much slip and will not lock the converter to save it self from breakage. I have tried different settings on Min. duty cycle and ramp rate for him without sucess. I'd try to raise the lockup to coinside with the 2-3 shift. This may allow the lockup when the defuel is in effect on the shift.

    My truck shifts perfect and the converter locks everytime, so I can't test theorys on it. Need more test subjects with big brass ones. The customer above, hooked up a manual lockup switch. This works to lock the converter, but throughs codes and you have no reverse until they are cleared.
    2013 LML, 550hp with factory emissions, stock cp4 and compound turbos.
    2002 LBZ, 4x4 (Max'd Out) 6000lbs 9.36 @ 154 mph NHRDA Champion and Record holder
    1965 El Camino, duramax 9.6 @ 149MPH

    All EFI tuned by Adrenaline Truck Performance

  8. #8
    Senior Member camcojb's Avatar
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    Quote Originally Posted by OSUBeaver View Post
    Not meant to be a dumb question, but do you mean "stops locking" like won't lock at any speed RPM, etc..... or just locks late?

    Or does it just spin like a mother from a stop like mine......... I hit 3500rpm on the 1-2 shift, 3700 right before it locks, then it shifts into 3rd and we're off to the races.

    Copilot doesn't do poop..... race mode or not.
    when it doesn't work which is more often than not, from a 4wd boosted launch it will not lock at all, at any speed. It always locks in normal or even "spirited" driving, as long as you are not wot. If it is locked at say 55 mph and you go wot, it unlocks at the downshift and never re-locks, again at any speed. Easy to see on the datalogs as the rpms on the 3-4 or 4-5 wot upshift only drop to 2800-2900 rpms after the shift instead of the normal 2500 rpms they would be at if the converter was locked. It also really slows the truck down.

    Jody
    07.5 4X CC 2500HD, EFI Live, MBRP exhaust
    new updated website!

  9. #9
    Lifetime Member IdahoRob's Avatar
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    Jerry yours is trying to lock in 2nd gear, but can't and blows threw the converter until it shifts into 3rd. This is what it looks like to me in the logs. I'll work you up a tcm tune to see about locking the converter on the 2/3 shift.
    2013 LML, 550hp with factory emissions, stock cp4 and compound turbos.
    2002 LBZ, 4x4 (Max'd Out) 6000lbs 9.36 @ 154 mph NHRDA Champion and Record holder
    1965 El Camino, duramax 9.6 @ 149MPH

    All EFI tuned by Adrenaline Truck Performance

  10. #10
    Senior Member camcojb's Avatar
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    Quote Originally Posted by IdahoRob View Post
    This is a problem for some trucks, and not just the LMM's I have a customer with a 700-800HP LB7 that is having the same issue.

    The TCM does see too much slip and will not lock the converter to save it self from breakage. I have tried different settings on Min. duty cycle and ramp rate for him without sucess. I'd try to raise the lockup to coinside with the 2-3 shift. This may allow the lockup when the defuel is in effect on the shift.

    My truck shifts perfect and the converter locks everytime, so I can't test theorys on it. Need more test subjects with big brass ones. The customer above, hooked up a manual lockup switch. This works to lock the converter, but throughs codes and you have no reverse until they are cleared.
    yeah, this 1058 is a bit looser I think than some of the other converters like the 1057, at least that's what I was told. That plus making even more power/torque gets the slip factor up there.
    07.5 4X CC 2500HD, EFI Live, MBRP exhaust
    new updated website!

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