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MY FIRST DRIVELINE PROBLEM!!! **how much shimming will i need?**

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by muddysub, Sep 23, 2002.

  1. muddysub

    muddysub 1 ton suburban status Staff Member Moderator GMOTM Winner

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    i don't know wether to cry or laugh, /forums/images/icons/crazy.gif i feel like a real wheeler now. /forums/images/icons/shocked.gif

    as some of you know i installed a set of hill shackles and i just ran it up and down my road in 4-hi and at about 30 mph i'm getting a noisy vibration. the CV is not hitting the crossmember so i assume it's the u-joint yelling at me for running at at that angle.

    obviously i need shims, so my question is will the shims that were on mudbogAD's jimmy with the 2.5" lift work for me or do i need a specific size? i have 4" springs and 1" hill 4wd shackles and a stock driveline.
     
  2. muddysub

    muddysub 1 ton suburban status Staff Member Moderator GMOTM Winner

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    Re: MY FIRST DRIVELINE PROBLEM!!!

    anyone? /forums/images/icons/confused.gif /forums/images/icons/frown.gif
     
  3. Shaggy

    Shaggy 3/4 ton status

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    Re: MY FIRST DRIVELINE PROBLEM!!!

    <font color="green"> You need whatever shims are going to make the pinion point about 2-4 degrees down from being right in line with the driveshaft... Hard to say exactly whcih ones that those are going to be.</font color>
     
  4. muddysub

    muddysub 1 ton suburban status Staff Member Moderator GMOTM Winner

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    Re: MY FIRST DRIVELINE PROBLEM!!!

    does anyone else have this setup? if so how much did you have to shim?
     
  5. Blazinaire

    Blazinaire 1/2 ton status

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    We installed the H4WD shackles on ducttapes K10 longbed with 4'' TC-HD springs. We left the axle where it was. Caster angle is more important than pinion angle on a DD. Does it handle the same as before better/worse? You could try a 2-3 degree shim for starters, that should get your pinion back up enough to cure your vibes. I would recommend taking it to an alignment shop and have them check your caster angle and go from there.
     
  6. trailblazer87

    trailblazer87 1/2 ton status

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    If you have rear blocks then you can replace them with angled blocks in the rear for pretty cheap. With 5" of lift I would be more worried about driveline length than angle. Your sub is long enough to not have angle problems until you get 8 or more inches of lift. What have you done to your d-line? If it is still the stock length then that could be the problem, not enough in the slip shaft letting it vibrate around a little.
     
  7. morphed86k10

    morphed86k10 1/2 ton status

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    The product review (done when Steve Fox was running the Hill Shackles) says that Brennan (sp?) Hill suggested a 3 degree shim...but Steve went with some 2.5's he already had, Rancho part number RS8125 with no problems.

    On a different note, did you measure exactly how much lift it gave you? The UAV gained 1 5/8 inches between the shim and shackles. I'm considering this go complement my 4" TCHD springs up front, and junking my rear blocks and 10 leaf one-ton springs for some 6" TC springs. Just not sure if the shackle alone will be enough up front. If if nets 5.5 total up front, thats close enough for me.
     
  8. Blue85

    Blue85 Troll Premium Member

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    Remember High School geometry? This is what it was for. Measure the distance between the spring eyes then find the difference in length of the shackles. Stock ones are 4", Hill's are 6" or more. Using the front spring eye bolt as the center of an imaginary circle, the rear spring eye has traveled in an arc a little more than 2". The circumference of the cirle is 2*Pi*(distance between eyes). Divide the arc length by the circumference and multiply by 360. This is how many degrees you have moved your pinion.
     
  9. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    OK Since you talking CV and CROSSMEMBER I believe you talking about the front drive shaft and I seem to recall your truck is still fulltime. 4 inch lift needs about a 2.5 degrees. That's what it took on my 75 and it ran down the road vibration free when it was still full time. With a BURB and a 203 you do not need to lower the t-case. plenty of rear driveline and lowering the case makes the angle on the CV worse. The reason being is your tilting the case down and the front output will point up more.
     
  10. muddysub

    muddysub 1 ton suburban status Staff Member Moderator GMOTM Winner

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    no i have an 89 with a NP241. i'll check on the 2.5deg shims
     
  11. k5blazerus

    k5blazerus 1/2 ton status

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    I have a six inch lift on my k20. I did the hill shackles too. I have I think 4 degree shims in the front. Every time I went wheeling and used 4wheel drive my driveline would make a not so good of a sound. So this is what I did.
    I did some work on the cross member and ground on the driveline stops. Now when I go wheeling The driveline dose not hit the cross member and the stops do not hit. If you want pictures I can get them.
    Colin
     

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