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91 Speedo out of wack!!

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by blazen91, Jul 17, 2001.

  1. blazen91

    blazen91 1/2 ton status

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    I went from 3.08's to 4.56's and now my speedo is way fast. I was doing about 40 and the speedo said 85!!! How do you fix this on an electric speedo? TIA.

    <font color=red>Land use issues are the heart of our sport.
    Get involved or lose the sport.</font color=red>
     
  2. HarryH3

    HarryH3 1 ton status Author

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    Just bolt on a set of 37 inch tires and it should read just about right. [​IMG] Otherwise you're looking at changing speedo drive gears at the t-case or installing a ratio adapter inline with the speedo cable. (Assuming a '91 even has a speedo cable. If it's totally electronic then you might need an adjustable VSS adapter from SuperLift.)

    <font color=black>HarryH3 - '75 K5</font color=black>
    <a target="_blank" href=http://www.angelfire.com/super/ThunderTruck>www.angelfire.com/super/ThunderTruck</a>
    It's a great day to be alive...
     
  3. blazen91

    blazen91 1/2 ton status

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    It has an electric speedo..... No cable!

    <font color=red>Land use issues are the heart of our sport.
    Get involved or lose the sport.</font color=red>
     
  4. K5Junkie

    K5Junkie 1/2 ton status

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    There is some chip or something that is in the dash somewhere that has to re-programed for the size tires and gear ratio you are running now.

    I also have a speedo that read fast b/c i went from 3.42's to 4.56 gears and 35" tires. So mine is not as bad as yours but it still reads about 10MPH too fast.

    <font color=red>'90 K5,7" lift, 35"BFG MT,15x10 Centerline Hellcats,350TBI,700r4,NP241</font color=red>

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  5. HarryH3

    HarryH3 1 ton status Author

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    You popped in while I was editing... [​IMG]

    (Assuming a '91 even has a speedo cable. If it's totally electronic then you might need an adjustable VSS adapter from SuperLift.)

    <font color=black>HarryH3 - '75 K5</font color=black>
    <a target="_blank" href=http://www.angelfire.com/super/ThunderTruck>www.angelfire.com/super/ThunderTruck</a>
    It's a great day to be alive...
     
  6. K5BLT4FUN

    K5BLT4FUN 1/2 ton status Premium Member

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    The device you have is a DRAC(Digital Ratio to Analog Converter). Check with Superlift or your GM dealer. I had a 91 Sub with the same problem and my local GM guy was able to get on made for me for about 100.00. Hope this helps.

    I may be slow, but I sure am fat!
     
  7. woody9

    woody9 1/2 ton status

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    just did the 3:54 - &gt; 4:10 14 boltFF myself, (along with jumping to 16" tires. Figure I'm 20% high on my speedo as well. 91 sub/350
    SUperlift sent me towards an elecronic plug in (good for 8-10 uses i think it is) for around $40 and a module you clip connectors on to get the correct reading. (18 for it if i remember). It's documented in part of their installation stuff and list the GM part numbers for it. Called my local and he said he'd need to order them. No biggie, but haven't gotten over to do it yet. Chasing down a driveline vibration first. then to the details like parking brakes and speedo!
     

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