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Speedometer Question?

Discussion in 'The Garage' started by WakeBoard&4X4er, Jan 15, 2003.

  1. WakeBoard&4X4er

    WakeBoard&4X4er 1/2 ton status

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    On a 91 K5 where is the pick up on the Speedometer? I think I was told that there is 2 of then, one on the Tcase and one on the Tranny. Is this right? On the 91 the Tcase is the 241. The Tranny is the 4L60? Here is real question, If I am Running 35s, and changing the rear Axle to 4.1 from 3.42s how will my Speedometer be off? I am not going to get it reset. Just want some ideas on how off it will be now.

    When stock 3.42s & 31s
    Now 4.1s and 35s
     
  2. nofeartruckin00

    nofeartruckin00 1/2 ton status

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    I don't believe that the axle gearing affects the speedometer, only tire size. The gears don't increase/decrease the distance you get out of one revolution of the tire. So the only change you will experience will be the 31"-35" jump. Atleast that's how I understand it.

    Went from 3.42 and 32's to 4.11 and 33's, and only the slight tire size made a difference in speedometer accuracy. And AFAIK, there is only one VSS, and it's in the tailshaft of the NP241.

    Hope that helps ya out.
     
  3. WakeBoard&4X4er

    WakeBoard&4X4er 1/2 ton status

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    " don't believe that the axle gearing affects the speedometer"

    I think it will because the drive shaft will spin at X RPM and the rear tires will turn slower then they did before. /forums/images/graemlins/thumb.gif

    But i might be wrong /forums/images/graemlins/confused.gif
     
  4. nofeartruckin00

    nofeartruckin00 1/2 ton status

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    I could be wrong too. But none of the speedo calculators out there take gear ratio into effect. I saw a small paragraph somewhere (real helpful hey?) that talked about speedometer changes, and I thought it said something about ratio not affecting the speed the VSS picks up. Let me do some more digging for ya.
     
  5. Sandman

    Sandman 3/4 ton status Author

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    </font><blockquote><font class="small">In reply to:</font><hr />
    I don't believe that the axle gearing affects the speedometer, only tire size.

    [/ QUOTE ]

    It most certanly does affect the speedo. If the speed sensor was on say the rim, then no there would be no change to the speedo with a gear change. But since it is in the transfer case it has a direct relation to it.
     
  6. nofeartruckin00

    nofeartruckin00 1/2 ton status

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    Wow, put me down for an Oops! If you double your gearing, your drive shaft would spin twice as fast as before, without a tire size change. I must have been thinking about distance traveled, not speed, Sorry! /forums/images/graemlins/ignore.gif I'll go sit in the corner, maybe shut up and listen is a good idea for me...... /forums/images/graemlins/1zhelp.gif
     
  7. WakeBoard&4X4er

    WakeBoard&4X4er 1/2 ton status

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    that is kool! just tring to get some info.
     
  8. zakk

    zakk 1/2 ton status

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    in the words of the infamous Marv Springer:

    "Speedo's are overrated"
     
  9. Sandman

    Sandman 3/4 ton status Author

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    Forget it! /forums/images/graemlins/grin.gif

    I havnt had my speedo hooked up for years.
     
  10. schmuck

    schmuck 1/2 ton status

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    changing gears will effect it, i do not know the formula but the inacuracy is a % so it will be less of a differance at lower speeds say if it is off by 3 mph at 20 mph it could be off by 9 mph at 60 mph
     
  11. Storm Trooper

    Storm Trooper 1/2 ton status GMOTM Winner

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    You could also try this? Digital Dash /forums/images/graemlins/grin.gif
     

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