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Just put on shackle flip, now vibration. Help

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by '73 K5, Jun 9, 2000.

  1. '73 K5

    '73 K5 1/2 ton status

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    I just drove around a little bit after I got my shackle flip put on the back. It drives nice, except I noticed it shakes when I decelerate with the brake applied. I'm sure its the driveshaft angles. I should just put some degree shims under the springs right??? How many degrees do I need and where can I buy them at.
    I have a SM465 and NP205 if that helps. Thanks.

    '73 K5
    Chevy good...Ford bad
     
  2. Burt4x4

    Burt4x4 3/4 ton status

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    Hmmm
    So your saying it only shakes when breaks are on and comming to a stop or slowdown?
    If so then the angle may be a good plce to start.
    I would get the same degree that comes on a 4" lift block.
    Don't know the numbe that degree but I bet it's all you need.

    Rock ON![​IMG] 72 K5 [​IMG] Led Zeppelin
    http://burt4x4.coloradok5.com
     
  3. HarryH3

    HarryH3 1 ton status Author

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    You need to get an angle finder (they have 'em in the tool department at Sears). Determine the angle of the output shaft on your transfer case and the angle of the pinion shaft on the rear end. The difference between the two is how much you need to shim the rear end. They should match within 2 degrees of each other to prevent driveline vibration.

    <font color=black>HarryH3 - '75 K5</font color=black>
    http://ThunderTruck.ColoradoK5.com
     
  4. Depdog

    Depdog 1/2 ton status Author

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    I used 2.5 on mine and it seemed to work pretty good, I think the biggest one you can get is like 4 degrees, either way neither one will put them back into speck, but should help out.

    Four Wheel Parts Wholesalers sells the shims, any 4x4 shop should have or be able to get them

    Depdog

    <font color=blue>"Lead, Follow, or BECOME the Trail"</font color=blue>
     
  5. MTPockets

    MTPockets 1/2 ton status

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    i also had a vibration due to improper driveline angles. i talked to stephen watson at ORD, what happens with the shackle flip is the pinion is turned too far up. the shims need are used to turn the pinion back down to within one degree of the center joint. remember: the pinion raises a degree under power, youll want to compensate for this. bottom line, i will be using a three degree shim to correct my vibration problem.
     
  6. Tommy

    Tommy 1/2 ton status

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    Has anyone considered lowering the front spring mount?? More lift plus puts pinion angle back in spec.
     
  7. Shawn

    Shawn 1/2 ton status Premium Member Author

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    You could also try to lower the transfercase so the ouput yoke degree matches closely to the axle pinion degree.

    Shawn
    87 K5
     
  8. '73 K5

    '73 K5 1/2 ton status

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    I always thought that lowering the T-case was an OK idea, but there are lots of people here who are against it. I did it a long time ago on a '79 Blazer and it never caused any problems. Anyways thanks for the advice y'all. I'm going to drive it a little more and then probably do the degree shims.

    '73 K5
    Chevy good...Ford bad
     
  9. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    I cut off the purches on the axle tube and rotated the pinion down 5 deg. I can run 70mph all day long and never a hint of vibration. The 75 runs smoother than the stock 79 with a part time kit. My truck is also still full time so I kept the case in the stock location so as not to create a problem with the front driveshaft. I run a TH350 and a NP203 case so I have a few inches longer drive line. That helps with the front shaft but hurts on the rear. You got to get that pinon angle changed to correct the problem.

    Diging it in the dirt with my K5's
    Grim-Reaper
    http://grimsk5s.coloradok5.com/
     

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