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  1. #1

    Default HELP with 2010 silverado

    I just installed a rough country 2" leveling kit and 2" replacement rear blocks and 2856518 nitto terra graps. The transmission is hestitant to shift to 6th gear, even holding it at a steady speed on flat ground. It used to shift up un-noticed. Now I have to let off the gas or set the cruise control for it to get to 6th gear, and it doesnt always do it. What do I have to do to get this fixed???

  2. #2
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    Red Z71 Max's Avatar
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    Default

    If you changed the diameter of the tire it changes the shift points. The computer is programmed for the stock tire size. You can get the shift points reprogrammed at a tuner. Most any shop that has a Dyno has the ability to do this. You will also notice that your speedometer is off also. You will need a speedo tool adjusting tool or use a gps for a true speed reading. Good luck

    (Scott) Myrtle Beach, SC
    January 2012 ROTM WINNER
    2011 GMC Sierra Z71 MAX 6.2 L w/ Trailering Package
    Rough Country, XD Rockstars, Nitto Trail Grapplers, N Fab, Lund Genesis, Putco, Gator Grip,
    Flowmaster 40 series, Diablosport InTune, Banks Ram Air CAI,
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  3. #3

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    actually, the speedometer is almost spot on now. It was a little fast. When I would pass a speed trap before the 285's, I would be at 60 and the trap would say 62 or 63. Now the same trap says 60 @ 60. On the roadside "measured mile" signs, I'm one half of a tenth off at a mile. So anywhere with a dyno can make these adjustments? I'll call the dealer tomorrow. Thanks

  4. #4

    Default

    Quote Originally Posted by undertheradar View Post
    actually, the speedometer is almost spot on now. It was a little fast. When I would pass a speed trap before the 285's, I would be at 60 and the trap would say 62 or 63. Now the same trap says 60 @ 60. On the roadside "measured mile" signs, I'm one half of a tenth off at a mile. So anywhere with a dyno can make these adjustments? I'll call the dealer tomorrow. Thanks
    What size tires did you have before installing the Nitto's??

    MIKE


    99"SILVERADO
    5.3 l 3.73 l G80
    BLACK BEAR CUSTOM TUNE
    SNUGTOP l COLORMATCH l KATZKIN










  5. #5

  6. #6

    Default

    I called the dealer last night, Duke Automotive in Suffolk Va, told the service manager what was going on and his response was "you cant put bigger tires on these new trucks, it messes up your transmission, antilock brakes, computer system and it voids your warranty. They are supposed to call me back today with a more educated response lol, that will depend whether or not I fly off the deep end or not.

  7. #7

    Default

    The Service manager was partially right, it does affect all those items but you can put larger tires, you'll need to have a dealer connect to the computer and adjust some settings.
    Standard dealer response to any mod is "voids warranty", this isnt correct, google "Magnusen Moss Act" and you should find a large amount of info on this subject, the only things affected on the warranty are items that the failure can be directly attributed to the modification.

  8. #8

    Default Update

    Ok fellers, I called the dealership (DUKE) and they informed me that they can NOT make adjustments because the tire size is larger than OEM allows. The shop foreman said GM only allows for 265/65/18 as there largest tire size. Another dealership (HALL) said they could do it and the shop foreman at DUKE cautioned me, saying that he doesnt have the software to do it, and if he did to have HALL print out the software because GM software doesnt offer 285's as an option.

  9. #9

    Default

    I'm guessing that you have the 3.08 gear package in the rear end and the 6 speed tranny? I think thats a bad combination IMO. I have the same thing in my 2010 and wondered if putting 285's on would have the same effect. I wish I didnt have that damn 6 speed tranny...
    2010 Silverado 1500 Z71 4x4

  10. #10

    Default

    There are programers to adjust your trans. and speedometer for tire size, I had a 2000 Silverado with 275/55x20's with AR Torque Thrust 2s at one time and used a Jet Speed Control Unit. Setting was at the limit for the ABS , They looked good but seemed heavy and rough ride plus hard on the brakes, sold them and returned to the OE's. Wasn't long after that had to have both hub assemblys replaced , check out the aftermarket magazines and web sites , transmission peformance.

    2012 Silverado

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