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Thread: NEWBIE! having trouble with new gears

  1. #1
    Tuner in Training
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    May 2015
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    NEWBIE! having trouble with new gears

    hello, I've owned hp tuners for about a year and this is all still rocket science to me. I put new gears in my truck it is 1999 chevy suburban 7.4l 4l80e on 40's (they measure 39.5) and switched from 3.73 to 5.38 gears. I changed the table but no table to change tire size any more? my speedo is way off it says im going faster then I am. I dont have a current log of truck but can get one in the day. Any help with this is appreciated. I'm not looking to have someone do it for me more or less explain what or where i'm wrong. Not that it should matter but truck has also been swapped with a np205 with a toner ring put in I think the toner ring was 41 count cant remember it is what ever it was stock ( just 1 vss instead of 3 or 4).
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  2. #2
    Tuning Addict 5FDP's Avatar
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    Looks like you can still edit both the tire size and gear size under the gear/tire wizard in the edit tab.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  3. #3
    Tuner in Training
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    May 2015
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    Seriously? I have been pulling my hair out for weeks to find this out?!!!!!!!!! Thanks alot!!!!!

    Next question my toner ring is 40 tooth count shouldn't my vss p ./rev-trans be 40?
    Last edited by onebigburb; 06-07-2016 at 09:48 PM.
    1999 chevy suburban 7.4l on 40's
    2006 chevy 2500hd duramax
    2004 chevy trailblazer wife's wheeler
    1999 ford f250 7.3l super duty
    2008 ford f350 6.4l super duty
    1994 chevy s10 4.3 vortech heads w/ tbi intake stock plan to bag one day
    2010 bmw 535xi wife's DD

  4. #4
    Tuner
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    Mar 2015
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    florida
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    110
    no I wish it was that easy theres a bunch of formulas that you got to factor in gear ratio/diameter of the tire whole bunch of crap... tire diameter x 63360 feet in a mile=revs per mile

    https://tiresize.com/gear-ratio-calculator/

    heres a calc id suggest you get the measurements from this calc or the manufactures specs of the same tire off their site but its always wrong never actual tire size even with proper psi.. do a roll out test mark a tire or use tape and make the pavement roll back one full revolution until the mark is straight down again make another mark measure it and that would be considered one revolution then times that by the 63360 and walla theres the actual tire diameter and not some kinda close guess like the specs they put up..good luck I check back later after work to see how your doin I wrote a ton of formulas down in a spiral and did all my math but now they changed the tire adjust so it doesn't estimate the calculated tire size now and I'm not sure what to do about that one
    Last edited by chevypower101; 06-08-2016 at 10:49 AM. Reason: i forgot to post the calc doh