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Thread: trans not shifting propely

  1. #1
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    Cool trans not shifting propely

    hey, I have a lb7/allison in a 76 camaro. Put a decent tune to it and now won't shift. Its strictly drag, and wondering if just programming can take care of this issue?
    Last edited by lb7/76camaro; June 13th, 2010 at 05:32 AM.

  2. #2
    Joe (Moderator) joecar's Avatar
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    I don't know anything about Allison's...

    but do post your before/after tune files, and any log files, so someone can take a look.


  3. #3
    Lifetime Member LBZoom's Avatar
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    Is it hanging up on the shift, or just shifting hard, or do the RPM's jump on the shift? It could be the gear ratio... what ratio are you running? The stock allison is programmed with 4.10, even though the Dmax trucks actually run a 3.73
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  4. #4
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    Did you reprogram the trans as well?
    Did it work before the updated tune was installed?
    If so, probably a tune error.
    Can you post the tune???
    2001 GMC 2500HD Duramax Allison, 4x4 ex-cab, 8' bed, 285/75R16, Sulastic rear spring shackles, Cognito upper control arm kit, Cognito Heavy Duty Tie-Rods, Cognito pitman and idler arm support kit, Heavy duty sway bar end link kit, Banks air cleaner kit with super scoop, AirDog 150 Fuel Preporator/Filter, EFI Live Tuning for power and fuel milage...

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    Just the engine trans did work good before. The tune was from the place I bought the programmer so should be no problem, but possible. Some reason the website won't let me post the program will try again later. Did have it out past sunday and changed the diff ratio helped but seems like its just missing the gears then enguaging. Ran a 12.29 with i think a governor still on cause it falls on its face at the top of the track.

  6. #6
    Lifetime Member LBZoom's Avatar
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    Quote Originally Posted by lb7/76camaro View Post
    Just the engine trans did work good before. The tune was from the place I bought the programmer so should be no problem, but possible. Some reason the website won't let me post the program will try again later. Did have it out past sunday and changed the diff ratio helped but seems like its just missing the gears then enguaging. Ran a 12.29 with i think a governor still on cause it falls on its face at the top of the track.
    Sounds like it's just de-fueling, check you base torque tables and see if they are still stock... if so raise them up in increments and see if that helps, the base torque table is responsible for the de-fuel effect. As far as why it fell on it's face, could be a rev limiter but sounds more like some other limiter, I'll wait to see the log before I make a suggestion there.
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  7. #7
    Lifetime Member THEFERMANATOR's Avatar
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    Quote Originally Posted by LBZoom View Post
    Is it hanging up on the shift, or just shifting hard, or do the RPM's jump on the shift? It could be the gear ratio... what ratio are you running? The stock allison is programmed with 4.10, even though the Dmax trucks actually run a 3.73
    The gear ratio settings in the TCM do not matter as to how it shifts. For some odd reason the GM engineers had all of the ALLISON TCM's programmed using the 4.10 ratio in them to calculate shift timing and such. When you change the gear ratio on the TCM you throw off ALL of the other tables along with it. And MOST of those tables CANNOT be seen by EFILIVE. When you change the gear ratio number you can also make it so the engine WILL hit the rev limiter before it shifts and cause it to fall on it's face. Most all of the big name tuners will tell you that the ECM is where you do most of your actual shift feel adjustments, and the only real changes to make to the TCM are shift point changes if your application calls for them.
    1995 GMC 2500 SUBURBAN powered by 01 DURAMAX/ALLISON, little of this, a little of that,
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  8. #8
    Lifetime Member LBZoom's Avatar
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    I changed the gear ratio settings in my TCM and didn't notice any change whatsoever, on my 2006 LBZ, I adjusted the shift timing. On the LB7 and LLY trucks with the Bosch ECM the base torque tables will limit the de-fuel seperately from shift timing of course. I believe the base torque table is the single biggest player in shift feel... as for changing the gear ratio affecting the limiter... I disagree with that, as long as all tables in the ECM and TCM are set to the same ratio then all is well I'd say, if you set the rev limiter at 4,000 RPM's it's still going to hit 4,000 RPM's especially if you haven't physically changed the gears. You're more likely to fall face first from hitting an underboost code or MAF code in my opinion.
    Peace Through Torque

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    Well every run I make its went 105mph no matter how it shifts or leaves the line. I changed the diff ratio to see if it would change anything, I gained 2mph and .2 of a sec. By changing the diff ratio I was just seeing if it would gain speed by having it think it was going the same speed but reving higher. Also I think its a speed limiter not a rev limiter. When you adjust the torque table how would you do it to help shift better and not take away to much?

  10. #10
    Lifetime Member LBZoom's Avatar
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    Well at full throttle you can probably max the base torque table out and get a good firm shift and not lose much on account of de-fuel because it's not going to cut you back as much. As far as for part throttle, you'll have to adjust in increments until you get the desired amount of de-fuel, personally I like a small amount of de-fuel for a more solid feel and smoother feeling shift. There is also speed limiter tables in the ECM under the speedometer segment, and I believe there are some in the TCM also but I can't remember for sure without looking.
    Peace Through Torque

    Punisher Performance DSP5 Tuning, PPE Dual CP3's, 68mm Fleece Cheetah, Punisher Built trans w/ Suncoast Parts, Airdog 165, SoCal 100% Overs, ARP Studs

    2013 NHRDA Sportsman World Champion

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