Speedometer is Off

Discussion in 'General Discussion' started by Bob D., Mar 20, 2019.

  1. Bob D.

    Bob D. New Member

    Messages:
    7
    Likes Received:
    5
    Joined:
    Feb 3, 2019
    Location:
    Franklinton, NC
    Hi Everyone,
    I’m new here as I just bought an 05 QC. I’m finding that the speedo is reading 6-7 mph faster (at highway speed) than I’m really going. My 1st thought was that the tire size must be off, but they are 305/40R22 which I believe are the correct stock size. So then I’m thinking I had to be gearing. Is there an easy way to tell if the gearing has been changed and what it might be? Is the best way to jack up the rear end and getting the ratio by comparing the wheel rotation to the driveshaft rotations? Could the tranny gears be different? Any thoughts?
    Thanks,Bob
     
  2. HemiLonestar

    HemiLonestar Full Access Member

    Messages:
    16
    Likes Received:
    0
    Joined:
    Dec 31, 2009
    Location:
    MD
    Gear change has no effect on speedo reading, only overall tire height/diameter. You have the correct OEM tire size so it sounds like someone mucked with the pinion factor in the computer. Easy fix, you can either correct it with a tuner or have a dealer do it. If you were in MD I'd offer to do it (I have a DRBIII). Pull your build sheet for fun: https://fcacommunity.force.com/RAM/s/equipment-listing
     
  3. shorty

    shorty Full Access Member

    Messages:
    2,016
    Likes Received:
    15
    Joined:
    Sep 1, 2012
    Location:
    Emory, Texas
    I once owned a '58 Desota---(you youngsters need to Google it) that read 220 on the speedo-----kilometers instead of miles. Great fun to show the guys I could run 150 with no problem. Then----dad had it change to the correct speedometer.
     
  4. HemiLonestar

    HemiLonestar Full Access Member

    Messages:
    16
    Likes Received:
    0
    Joined:
    Dec 31, 2009
    Location:
    MD
    De Soto lol? My grandparents had a De Soto Suburban. Was yours an export that came back?
     
  5. shorty

    shorty Full Access Member

    Messages:
    2,016
    Likes Received:
    15
    Joined:
    Sep 1, 2012
    Location:
    Emory, Texas
    No, my dad, a lawyer, did some work for the Chrysler dealer (Desota) so bought cars from him. The station wagon (forerunner of the minivans) had been intended to go to Europe. Man It would run, especially for a kid of 14----yeah, in Texas we got our drivers license at 14 which turned out to be real dump on their part. I had 21 moving violations when I went to Nam.
     
    HemiLonestar likes this.
  6. HemiLonestar

    HemiLonestar Full Access Member

    Messages:
    16
    Likes Received:
    0
    Joined:
    Dec 31, 2009
    Location:
    MD
    Go big or go home lol