Allison Trans discussion

Discussion in 'Tow Rigs and Trailers' started by 77GreenMachine, Apr 1, 2019.

  1. 77GreenMachine

    77GreenMachine Phillip Talton

    Joined:
    Mar 30, 2010
    Location:
    Trinity, NC
    For the sake of discussion...

    Talking with a buddy about buying an 05’ 8.1/Allison truck. I shared my only experience with an Allison which is this:

    03 Duramax (LLY), towing a TJ to Harlan. In Tow mode, if I was going down hill and got on the brake just a little to slow down and I just rode the brake for a little to maintain speed the Trans would gear down, which I know it’s supposed to do. But several times it geared down to the point of red lining the truck. Since I was unfamiliar with this, it scared me and I didn’t want to hurt the truck so I would give it gas and it just redlined it more, so I’d scramble to get it out of tow mode.

    My question is:
    (1) was it ok to rev that hard?

    (2) Was it my fought for “riding the brake” like I was?

    (3) does the Allison behind the 8.1 gas engine have the same characteristics as behind the Duramax?
     
  2. Mac5005

    Mac5005 Welding Instructor

    Joined:
    Oct 19, 2005
    Location:
    Rocky Mount
    In tow mode, I’ve had the 6Lxx do the same thing. I’ll usually opt for manual mode and use the selector button once I get off flat ground.

    Not sure the total difference in programming between the Allison and 6l series, but I’ve had the exact same experience.

    Tow haul mode being too aggressive on downshifting in breaking. One thing is to down shift early to stay off the brake pedal and use more compression braking.
     
  3. 77GreenMachine

    77GreenMachine Phillip Talton

    Joined:
    Mar 30, 2010
    Location:
    Trinity, NC
    I haven’t had that problem with my 6.0/4L80. I do pull it down in 3rd on rolling hills for that help. The selectable shift didn’t come out till 11’ I believe.

    Probably what I should have done with the Allison, but I just let tow mode do it’s thing.
     
  4. Mac5005

    Mac5005 Welding Instructor

    Joined:
    Oct 19, 2005
    Location:
    Rocky Mount
    I believe the manual shift selector started in 07/08.

    The 4spd tow haul programming is much less aggressive than the 6spd.

    My 4L85 would never downshift on braking in tow haul.
     
  5. CarolinaHD

    CarolinaHD Well-Known Member

    Joined:
    Dec 2, 2008
    Location:
    Mt. Pleasant NC
    1. Yes
    2. No
    3. Yes


    GM moved the red line on the gauge clusters starting in 2006 because of this same issue; customers were concerned/complaining/freaking out because it went over the red line.

    Duramax cuts fuel at 3200rpm and can rev up while engine braking to 4800rpm.

    Not sure about the 8.1

    Manual mode for the Allison started in 2006.
     
  6. Tim C

    Tim C Wizard

    Joined:
    Jan 22, 2007
    Location:
    Fayetteville
    As long as no aftermarket tuner has been installed, I don't believe they would allow a tune that would allow the engine to grenade itself. Especially if they are providing a warranty on that engine.

    Fwiw my dad has complained about his 06 dmax reving high on downgrades in tow haul mode, I told him the same thing and said to let it do it's thing.
     
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  7. BigClay

    BigClay Well-Known Member

    Joined:
    Sep 24, 2008
    Location:
    Winston-Salem
    Just tell him to get a Cummins and be done :D
     
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  8. upnover

    upnover Grumpy, decrepit Old Man Moderator

    Joined:
    Mar 20, 2005
    Location:
    Morganton NC
    I have a 02, 8.1 and an Allison. The tow haul part doesn't work. But it still gears down. Maybe not as aggressively as you describe. But it does gear down. That, along with my trailer brakes, I have no issues of over revving or going too fast. Coming down Old Fort Mnt, I can keep it between 55-60 with ease. Most of the time, I just pull it down out of over drive.
     
  9. 77GreenMachine

    77GreenMachine Phillip Talton

    Joined:
    Mar 30, 2010
    Location:
    Trinity, NC
    Those models are really bad about the shifter pinching the yellow wire for the Tow Haul button. If you remove the plastic on the lower portion of the steering column (just a couple screws) you can see the yellow wire. Just splice it back together and you’re good to go. I have fixed 3 of them so far!
     
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  10. Croatan_Kid

    Croatan_Kid How's your hammer hangin'?

    Joined:
    Nov 4, 2007
    Location:
    New Bern
    An 03 is still an LB7. They downshift because they don't have a VGT turbo to help as an engine brake. They also have an anti coast clutch that helps keep the truck from gaining excessive speed when you're not on the throttle.

    I couldn't imagine hauling anything heavy without the tow/haul working...it's sooo much better when the converter locks in second and stays locked.
     
  11. 77GreenMachine

    77GreenMachine Phillip Talton

    Joined:
    Mar 30, 2010
    Location:
    Trinity, NC
    I agree! @upnover for such a simple fix, better check it out. You’d be much happier with the towing if you think it does fine now.
     
  12. a_kelley

    a_kelley mechanical fixer

    Joined:
    Jan 26, 2010
    Location:
    Rutherfordton
    Heck if you want to be lazy, advance sells the complete lever with new wires.
     
  13. Jody Treadway

    Jody Treadway Croc wearing fool Moderator

    Joined:
    Mar 20, 2005
    Location:
    Hendersonville, NC
    Where is the tow/haul switch on my G56 Cummins?
    Can't find that bitch anywhere
     
  14. skyhighZJ

    skyhighZJ Thanks for your taxes

    Joined:
    May 31, 2012
    Location:
    Fort Polk, La.
    Yours is more complicated to activate.
    1.) depress left foot pedal
    2.) maneuver right hand lever thingy device to a position of lower numerical value as seen at the top of said lever thingy
    3.) release left foot pedal to upright position
    4.) repeat as necessary.
     
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  15. a_kelley

    a_kelley mechanical fixer

    Joined:
    Jan 26, 2010
    Location:
    Rutherfordton
    this g56 transmission is so advanced, it's mind controlled. It changes when your brain tells your hands and feet exactly what changes to make and when. It needs no tow/haul switch to accomplish any of the users desired results. Exactly what the user envisions, is accomplished merely by thinking about it.
     
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  16. Tim C

    Tim C Wizard

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    Jan 22, 2007
    Location:
    Fayetteville
    Pretty sure it's the R position.
     
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  17. CasterTroy

    CasterTroy Motarded

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    Mar 21, 2005
    Location:
    Wallburg
    And just like that, cummings superiority enters the thread

    images (3).jpeg
     
  18. jeepinmatt

    jeepinmatt Still Fat

    Joined:
    Mar 24, 2005
    Location:
    Stanley, NC
    Fun fact: The LB7/LLY Allison 1000s have a 6th gear that is not utilized by GM. Might also be true for the 8.1s.
     
  19. Croatan_Kid

    Croatan_Kid How's your hammer hangin'?

    Joined:
    Nov 4, 2007
    Location:
    New Bern
    The 8.1s do too. The conversion isn't really worth it when you break it down. The price has come down some, but it's still pretty damn expensive.
     
  20. jeepinmatt

    jeepinmatt Still Fat

    Joined:
    Mar 24, 2005
    Location:
    Stanley, NC
    I'm still unable to comprehend why they would have a transmission that was mechanically equipped with 6 speeds, but only utilized 5 :confused:
     
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  21. 77GreenMachine

    77GreenMachine Phillip Talton

    Joined:
    Mar 30, 2010
    Location:
    Trinity, NC
    Go ahead and do all your R&D, engineering and production cost, flood the market and sell like crazy with the 5 speed. Design is already done so you change a couple parts and programming after a few years and flood the market all over again for all the folks that just HAVE to have that 6th gear!

    Pure speculation on my part.
     
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  22. Croatan_Kid

    Croatan_Kid How's your hammer hangin'?

    Joined:
    Nov 4, 2007
    Location:
    New Bern
    It would be sweet if I had 6th on my truck and geared it 4.10 with the 33s. I'd get better low end and still have the same final drive as I do now. 5th is .71 and 6th is .61.
     
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  23. shawn

    shawn running dog lackey of the oppressor class Administrator

    Joined:
    Mar 13, 2005
    Location:
    Raleigh, NC
    If it's like the Fords, you conceptually have a 3-speed reduction gearbox mated to a 3-speed overdrive gearbox. The final drive gear ratios are created by different combinations of front/rear gear, but there are actually up to 8 possible combinations (assuming there's a 1:1 ratio in both boxes).
     
  24. NickMaul

    NickMaul Well-Known Member

    Joined:
    Jul 4, 2009
    Location:
    Virginia Beach
    Chrysler did that with the auto behind V8s in the WJ. I think you could have the dealer do some re programming to get the extra “gear”


    Sent from my iPhone using Tapatalk
     
  25. Jody Treadway

    Jody Treadway Croc wearing fool Moderator

    Joined:
    Mar 20, 2005
    Location:
    Hendersonville, NC
    Yup.
    The very early 545RFE gained an additional gear in between D and OD so when you kicked it down it had an appropriate ratio so it wouldn't lug or scream.
    Was just a simple PCM flash
     
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