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Fixing I my Speedo for 35's I need...?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by MudNurI, May 19, 2002.

  1. MudNurI

    MudNurI 1/2 ton status

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    Fixing I my Speedo for 35\'s I need...?

    Okay this speedo thing being WAY outta wack is really getting to me..Can someone tell me exactly what I need to fix it. I think its some gear for my transmission? (haven't a clue?).....its an 86 K5 -4 speed, 305.

    thanks
    Brandy
     
  2. FWP

    FWP CRS

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    Re: Fixing I my Speedo for 35\'s I need...?

    There are 2 plastic gears located inside the rear output housing of your T-case. One is a helical drive gear that is slid on the ouput shaft. The other is the driven gear, that turns the speedo cable attached to the housing. Not sure of the exact part numbers, but you can get them from a GM dealer fairly inexpensive. To make it close, you change the gears to a different tooth count to make the speedo cable turn faster to make up for the tire size. The dealer should be able to help you figure the correct gears. That's the method I used on my '81. I have heard somewhere that the speedo inside the instrument cluster can be adjusted, but I don't know how that method works. HTH
     
  3. rusty79

    rusty79 1/2 ton status

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    Re: Fixing I my Speedo for 35\'s I need...?

    there is actually a shop near me that calibrates it for you the put your vehicle on roller looks like a dyno then they just run it it up and they have thier own gauge to judge it by then they just count the teeth like in the above post and swap it out you can figure it out on paper but this way is as precise as stock its a bit pricey at about 100$ but worth it to help keep you out of trouble
    Dave
     
  4. MudbogAD

    MudbogAD 1/2 ton status

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    Re: Fixing I my Speedo for 35\'s I need...?

    I kinda have this problem, just backwards. I just got the 4.56's and now the speedo says 70 when I'm going 45. It sucks, I guess I need bigger tires.
     
  5. Blazinaire

    Blazinaire 1/2 ton status

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    Re: Fixing I my Speedo for 35\'s I need...?

    Same thing here, I thought I was goin' slow! 4.56's with 35''s, maybe some 38''s will fix my speedo, that would be money better spent! Maybe in 40,000 miles when my tires wear out.
     
  6. MudNurI

    MudNurI 1/2 ton status

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    Re: Fixing I my Speedo for 35\'s I need...?

    That's my problem... if I were to get up on the highway- and do say 60ish,,my speedo would be PEGGED... I have 3.73's..and 35's. I thought (???) these were the gears/axles that came stock on this thing, but wouldn't my big tires make my speedo SLOW?..

    Brandy
     

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