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90-91 Blazer/Jimmys w/ABS

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Udy, Apr 4, 2000.

  1. Udy

    Udy Registered Member

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    fairport NY
    I need acurate information on what needs to be done when changing gear ratios and tire sizes on ABS equipped Blazers. I've heard these models have an electronicly controlled speedometer. A guy at work says he knows how to reprogram something under the dash whenever he changes tire sizes. Anyone able to help? thanks.
     
  2. CK5

    CK5 In my underwear Administrator Premium Member GMOTM Winner Author

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    I had mine (1990) changed by De Luxe Speedometer here in Denver (303-629-6958), there is a series of plastic gears that have to be changed and I do believe the box that holds these gears are under the dash.

    Steve
     
  3. Crash90K5

    Crash90K5 Registered Member

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    I put in a slip-yoke eliminator in my NP-241, and the first thing JB Conversions asked me was do I have a mechanical or electrical speedo... How the hell do I know? Crawled up under there and found... It's electrical. When I pulled apart the case, after getting the tailshaft housing off, the first thing to pull off was the speedo gear. There are different sizes that you can get. Can't help you on what size [​IMG]. I think 1 tooth = 5 mph / bigger = faster. Good luck

    Steve - do you have a mechanical speedo?

    [​IMG] <font color=blue>Crash90K5</font color=blue> [​IMG]
     
  4. 6.2Blazer

    6.2Blazer 1/2 ton status

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    I haven't had any problems (that I know of) on my '90 and I currently have 4.10 gears and 35" tires. I know on newer models with the OBDII (starting the mid to later '90s) that it is necessary to reprogram the computer to compensate for gear or tire size changes, as it will make a huge difference in how the engine and transmission operate. I knew a guy with a '97 or '98 Chevy who put in 4.56 gears and 35" tires, the thing wouldn't hardly run on the road until the computer was recalibrated.
     

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