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Safe Way to do this?

Discussion in 'The Garage' started by jc71355, Feb 22, 2003.

  1. jc71355

    jc71355 1/2 ton status

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    I'm having speedo issues right now so I looked in my manual and it says to test the Speed Sensor by jacking the truck up, puting it in gear and reving it. This doesn't seem very safe to me for the simple reason that I don't start having problems till I hit 45-50 mph /forums/images/graemlins/blush.gif Would this be safe to do on jackstands? Sorry I just have the mental pic of my truck falling off the stands due to vibrations. Also am I going to have to get this thing up to the same rpm and gear as I do with it on the ground, or will it get there quicker b/c I don't have a load on it?
     
  2. willyswanter

    willyswanter 1/2 ton status GMOTM Winner

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    I seriously would not do that on jack stands... A rolling chassis dyno yes, but not jack stands. Whats the difference of that and driving down the road? Why can't you test it while driving down the highway?
     
  3. jeffro

    jeffro 1/2 ton status

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    Wrap a snatch strap around your neck and hook it up to the bumper so you won't lose your truck if it does take off on you. /forums/images/graemlins/grin.gif

    Disclaimer: Just kidding!! /forums/images/graemlins/deal.gif
     
  4. Dale fan

    Dale fan 1/2 ton status

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    You should be ok. Just make sure it is setting good on the stands, you might rock it a bit just to see. With it off the ground it won't take much reving to get it to 40-50 mph. Just dropping it in gear at idle will get around 20 or so since there is no resistance on the wheels.
     
  5. cybrfire

    cybrfire 1 ton status Vendor GMOTM Winner

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    I agree with Dale fan. Should be ok and do the rockin thing. If you need to simulate a load you can apply the brakes. Also I'm not so sure it will shift without a load. Never actually did this but i think you could rev the p out of it with out getting a shift. Just thought I might add that.
     
  6. jc71355

    jc71355 1/2 ton status

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    The reason I can't do it while driving down the road is b/c I have to read the Volts comeing off my speed sensor down on the Transfer Case. I think I will try jacking it up first and rocking it to see how stable it is. Shifting is my main concern, sometimes that thing can shift pretty hard.

    Thanks Ya'll
     
  7. willyswanter

    willyswanter 1/2 ton status GMOTM Winner

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    So your going to be under the truck while it's going 50mph on jack stands /forums/images/graemlins/shocked.gif
     
  8. Dale fan

    Dale fan 1/2 ton status

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    Well like cybrfire said, I am also not sure if it will shift without the load, someone should know though. If it does I would thnk that it wouldn't be to harsh since there would be no load.
    Willys was typing while I was and he made a good point, get some jumper wires to run from the sensor to your meter. i would hook it up and then sit in the cab while giving it gas with my other foot on the brakes just in case. You should be alright and I would do it if I couldn't find someone with a frame lift I could borrow, just throw every stand you got under the frame.
     
  9. jc71355

    jc71355 1/2 ton status

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    /forums/images/graemlins/shocked.gif Heck No, I ain't that crazy /forums/images/graemlins/shocked.gif I will hook the meter up and run it out from under the truck and then start it and do the test.
     
  10. RedBrute

    RedBrute 1/2 ton status

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    Jack stands, block both fronts in front and rear and remove the rear tires/wheels. If it comes down, the brake drums won't drive it anywhere.
     
  11. BowtieRed

    BowtieRed 1/2 ton status Author

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    That's what I was going to say- take off the tires and wheels, and put something under the axle so that even if the jackstands fail the drums still will not touch the ground. I have had a truck fall off jackstands, luckily pieces of wood were place under the truck, by chance, so that the pumpkin never hit and only one drum touched, but no damage was done.
     
  12. Chris_T

    Chris_T 1/2 ton status

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    What about unhooking the shafts and just running the T-case output? You couldn't brake the T-case this way, so you'd have to do your test, shut off the truck and wait for everything to stop rotating before you put the trans back in park. Otherwise you'd be looking for a new park sprag.
     
  13. chulisohombre

    chulisohombre 1/2 ton status

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    i was thinking what chris said.in two wheel drive you could take out the driveshaft and just the rear yolk on the transfer would spin and you wouldnt have to worry about anything falling down
     
  14. Z3PR

    Z3PR Banned

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    [ QUOTE ]
    The reason I can't do it while driving down the road is b/c I have to read the Volts comeing off my speed sensor down on the Transfer Case. I think I will try jacking it up first and rocking it to see how stable it is. Shifting is my main concern, sometimes that thing can shift pretty hard.

    Thanks Ya'll

    [/ QUOTE ] I think I'd pay a shop to do it. /forums/images/graemlins/eek.gif /forums/images/graemlins/eek.gif /forums/images/graemlins/eek.gif
     
  15. Chris Demartini

    Chris Demartini 1/2 ton status

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    <font color="blue">I agree with taking out the driveshaft. What is the problem your having?
     
  16. jc71355

    jc71355 1/2 ton status

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    My speedometer is bouncing causing my truck to run poorly.
     
  17. One_Ton_k5

    One_Ton_k5 1/2 ton status

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    If you are going to run a wire out from under the truck, why not just run it into the cab and drive down the road. That would be a lot safer.

    Later.
     

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