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rear end shake

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BlueOx, Sep 26, 2000.

  1. BlueOx

    BlueOx 1/2 ton status

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    When I take off from a stop light and give it some good gas the rearend shakes form left to right real bad of a few feet. Now, if I ease into the gas that shaking dose not happen. Its not a wheel hopping effect; it more a back and forth effect.
    Can anyone help me; its driving me crazy.
    Thanks
     
  2. bigdaddy89

    bigdaddy89 1/2 ton status

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    Your driveline is probably the problem. I had a cv joint style driveline made for mine and the shaking and vibrations went away. Try Dick's Driveshafts located in AZ.
     
  3. BlueOx

    BlueOx 1/2 ton status

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    after a few feet all the saking goes away. it's just when i take off hard. I dont think it is that drive line
     
  4. bigdaddy89

    bigdaddy89 1/2 ton status

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    Mine was doing the same thing. Your pumpin is moving up when you take off from a light, causing the driveline to be at the wrong degree angle. How much lift do you have?
     
  5. Emmettology 101

    Emmettology 101 3/4 ton status

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    Have you checked to make sure everything is tight?(u-bolts, wheels, driveshaft, springs..) Also check your pinion bearings and axle bearings...

    HTH

    Mike [​IMG]
    See <font color=green>EMMETT</font color=green> -&gt; http://emmett.coloradok5.com
     
  6. Blue85

    Blue85 Troll Premium Member

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    It sounds like axlewrap. When you're on the gas in 1st gear is when the most torque is being passed to the rear end. While your driveline angles may be fine for the rest of your driving speeds, at this point they are probably off.
    There are several ways to deal with axlewrap, if it is your problem:

    -Get rid of your blocks. When there is a block between the axle and spring it gives the axle a bigger mechanical advantage to twist the spring and change the pinion angle. You have to replace the blocks with lift springs or do a shackle flip.

    -Add ladder bars. This eliminates axlewrap completely but also eliminates a lot of flexibility. Good for on the road. Bad for off road.

    -Shim the axle. You put little wedges between the axle spring pad and the spring to change to move the pinion up just a degree or two. This makes the angle more correct under high loads without making it too high for normal driving loads. You have to make sure that you have long enough center bolts, though.

    -Add a torque arm. These are a modified version of a ladder bar that does not limit axle articulation. I believe that they are patented and only available from one source, the name of which I can't remember, of course.


    It is also possible that something is a little loose inside the axle. Is it a 10-bolt? You might also want to check your transfer case to cross-member mount and make sure that it is still one solid piece. If that is loose it can let the whole drive train shimmy a little bit under heavy load.

    '85 JIMMY
    '90 paint/grill/trim 5"susp 33/12.5/16.5
    Fresh 350 B&M '87 TH700
     
  7. BlueOx

    BlueOx 1/2 ton status

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    I only have 3" blocks in the rear to level it out. The drive shaft does look to be at a bad angle though. It looks to be sticking out of the t-case alot. how can I fix this. i ahve friends that have bigger lifts and are doing fine.
     
  8. Heath-La. 89GMC

    Heath-La. 89GMC 1/2 ton status

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    U-Joints.... and get some more pitch in that rear end
     
  9. Blue85

    Blue85 Troll Premium Member

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    With knowledge comes power. You're going to have to figure out what angle the front u-joint is operating at and what angle the rear u-joint is operating that. I would aim for the rear one to have one degree less angle than the front one. When I say front and rear, I mean the U-joints at either end of your rear driveshaft. You can get ahold of an angle finder or take a bunch of measurements and use geometry to find the angles. Once you know what angle you're at, you can choose the right shim for the rear axle. Should cost $20 for a pair. Make sure that you install them correctly so that the spring center bolts still locate the spring in the hole in the axle spring pad.

    '85 JIMMY
    '90 paint/grill/trim 5"susp 33/12.5/16.5
    Fresh 350 B&M '87 TH700
     
  10. Blue85

    Blue85 Troll Premium Member

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