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Thread: '05 GTO Speedo Issues

  1. #1
    Potential Tuner
    Join Date
    Oct 2011
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    1

    '05 GTO Speedo Issues

    OK, so I've had nothing but problems trying to get my speedometer to read correctly. It's been going on for about..well almost 8,000 miles according to my horribly inaccurate odometer! haha

    Details
    2005 GTO 6-Speed
    3.89 rear gear DSS 9-inch conversion.
    *built trans at the same time as rear*

    I've changed the gear value, nothing. The tires, nothing. Then I tried an SCT handheld that simply asks you what gears you have so it's fool-proof, NOTHING!

    HP Tuners will read and write correctly and the changes are going in, but the speedometer and odometer are showing the incorrect values. Approximately 10mph off.

    I'm being told I have to recalibrate my DIC, but I don't know how or where to do that. Could anyone shed some light on what I could possibly be doing wrong with this car?

    Thanks,
    Kevin

  2. #2
    I am running into a similar issue but with 4.11s. I am playing with tire sizes now and verifying via tomtom. It changes it more than me just telling it what gears were in it. I was ten to 12 mph off at first, flashed in 4.11 value and I was down to 7 off. Changed the tire height and the Revs per mile setting and i got down to 4 mph off.

    Owner/Tuner Street Performance Syndicate

    06 GTO: D1SC , Full Suspension, 23X .6xx lift Ed Curtis Cam, Mast Heads, Gforce 9" 4.11 Gears, Holley High Rise, Stage 12 Fuel System, Boost By Gear

    01 Duramax: Blown Tranny (again) BWs467 Turbo, Head Studs, Exergy Injectors, Lift Pump, Moonshine
    2014 Taurus SHO: (Wife's Car) OR DPs, Tuned, CAI
    2006 TBSS; AWD SLP Catback, K&N CAI, Tuned

  3. #3
    Advanced Tuner vette_c6's Avatar
    Join Date
    Jun 2008
    Location
    Kuwait
    Posts
    390
    why dont you upload your file here

    and give me your Exactly Tire number with your Axle number

    let me see it please

    specialize in: V8 Tuning (Kuwait)
    Abdullah Al-najdi
    00965 99369929
    www.youtube.com/alnajdi83
    Tuners ! Quit Raping your PE TABLE !
    instagram : alnajdi83
    best number in 1/8 mile 4.54 ( My Driving + My Tune ) !

  4. #4
    Potential Tuner
    Join Date
    May 2012
    Location
    Cali
    Posts
    8
    I had the same issues when I changed my CTS-V from the stock 3.73 to a 3.42 rear diff. It would display 71 mph at 2000 rpm, but my GPS was showing an even 80. My mileage was also coming up short as it was not counting correctly. You're right about the gear ratio box doing nothing; you'll have to modify your VSS output pulses per mile.

    To do this, devide the displayed mph by the actual mph (i.e. 71 / 80 = 0.8875), then multiply your VSS output pulses by this number. Insert that number as it will be the actual pulses required for your speedo. After doing this to my -V, my speed now displays within .1-.2 mph of the GPS.

    Give it a try and let me know how it works.
    Last edited by Velocity²; 06-08-2012 at 12:14 AM.