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Thread: LBZ gear change

  1. #1
    Lifetime Member IdahoRob's Avatar
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    Default LBZ gear change

    I've got a customer running 4.88 gears on a LBZ. Anyone tried changing H0103 then putting in the actual tire size and have it work.

    Or should I just do the calculations and leave the gearing stock?

    Thanks,
    Rob
    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

  2. #2
    Junior Member
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    I still didnt get it to work, I had to use my GPS and lots of trial and error, what size tires is he running? if its 285's (which I doubt) I can post the numbers for you.
    2005 GMC Sierra ec/lb LLY - stock-

  3. #3
    Lifetime Member IdahoRob's Avatar
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    37". I'd think there is some kind of calculation, but not sure about converting it to LBZ "tire rev. per mile"
    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

  4. #4
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    yeah i had that problem, it changes a few value but not all. I just used the GPS and thats about all i could figure out...sorry i cant help more :(
    2005 GMC Sierra ec/lb LLY - stock-

  5. #5
    Lifetime Member IdahoRob's Avatar
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    Thank-you for the help. I did find a speedo calc. that you can import gear ratio, tire size, and RPM, and it gives you speed.

    I then just did some math to find the difference and then modded it for stock gearing and the matched tire size to = the same MPH.
    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

  6. #6
    EFILive Distributor Trippin's Avatar
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    I did one last week. 37" with 4.56 gears. I entered the gear ratio and then corrected the tire size.

    A Tech 2 to reprogram the ABS to 285-75-16. Quick trip around the block to verify with a portable GPS and off he went.
    www.socaldiesel.com



    EFILive-DSP5......Switch your Attitude!
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  7. #7
    Junior Member Donovan's Avatar
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    Thanks for the Info on this guys. Perfect timing as I just swapped in 4.56s on my setup (today) with 37s and changed H0103 to 4.56 and H0136 to 570 ( from stock 682) and it's perfect as far as my GPS is concerned.

    I did the Tech 2 trick a couple of years ago and so far no abs lights or CEL/DTCs.
    Last edited by Donovan; March 28th, 2008 at 02:31 PM.
    E35A/A40 + DSP5

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