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WIll this cure those rear end vibration issues ?

Discussion in '80-Series Tech' started by Beast II, Nov 5, 2003.

  1. Beast II

    Beast II

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    I'm not a mechanic, but thought this looked interesting. Could it cure those rear end vibration issues ?

    http://www.bigballsoffroad.com/prod387.htm
     
  2. IdahoDoug

    IdahoDoug

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    Beast,

    No. If your vibrations are from the rear shaft almost falling out, then yes. But if that's the case they'd have wiped out in just a few weeks of driving.

    Vibrations in lifted vehicles are almost invariably related to the increased angle of the drive shaft joints. The more the angle, the greater are the axial forces due to the design of the joints. You can cure it by rotating the axles so that the angle is reduced again, or by installing double cardan joints that are able to handle greater working angles.

    Doug
     
  3. DanKunz

    DanKunz SILVER Star

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    I believe that product exists due to the aussie crews having MUCH larger lift heights.
     
  4. lc1996

    lc1996

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    I know this is an old post, but I'd like some clarification on this issue since I have a little vibration w/ 6" lift.

    Correct me if I'm wrong, but I thought that to minimize having any vibration in your drive shaft you want both ends of joints to have the same angle so that they cancel each other out. Unless of course you have a double cardan joint shaft.

    Carl
     
  5. robbie

    robbie Guest

    That product will not doing anything except help with the slip joint from falling out. If you have a 6 inch lift with nothing but stock bumpers (ie no extra weight other than stock) your lift will be higher. So my question is what year, how's lift, what other things do you have on your truck, what weight do you carry in the back?
    Other questoins? do you feel it in the seat of your pants or in the steering? Is it more of a vibrations or a sound you hear? later robbie
     
  6. lc1996

    lc1996

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    Robbie,
    It's actually a humming noise that I have. My '96 has Slee's complete 6" Kit, 315/75R16 on 16x10 rock crawlers, Kaymar rear bumer w/tire carrier and full spare, gas can carrier, custom sliders off George's design, and stock frnt bumper. The only time I really hear it is when some of the load is off the drive shaft. For example, when I'm driving on the freeway and I let off the gas, but then apply just a little pressure you can hear the humming noise. Even if I'm towing my 3600lb boat I don't hear the hum, unless I do the following procedure above. Oh, the noise is coming from the center console area.

    My concern is if there's a vibration issue with the shaft, will it wear out the joints faster and/or will there be harm in the long run on the 3rd member and t-case?

    Carl
     
  7. robbie

    robbie Guest

    Did you install the lift? fi so did you max out the adjsuter on the upper control arms in the rear? Did you have the u-joints checked? Some times older u-joints that have worn in one positions and then drastically change will create a hum like you are describing. If the u-joints are OK then I think you would be a canidate for the CV style drive shaft. vibration can create some extra wear on the input to diff bearing and the out put bearing in the t-case. hope this helps you, later robbie
     
  8. Safado

    Safado

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    Carl,

    Welcome to the board and the club...check out this thread.

    https://forum.ih8mud.com/showthread.php?t=17536

    This is how I understand it from that thread, Slee, and other drive line shops I'v chatted with.

    When you lifted your truck, the rear pinion is forced down. The more you lift it, the more the tilt in the rear pinion and the more the transfer case and pinion become out of plane with each other. Under normal acceleration, the torque on the pinion causes it to raise...thus decreasing the angle, and conversly when you decelerate the pinion is torqued in the opposite direction giving you more of an angle offset than you have sitting still. This is why you only get it decelerating from high speeds, and why applying a bit of gas causes it to suside. Slee sells adjustable upper controll arms to allow you to lengthen the stock arms and move the pinion back to its stock configuration. This very well may get rid of the vibration. If not, the same adjustable arms can be used to shorten the stock arms and point the pinion up the the t-case in which case you can use a CV joint in the rear driveline to eliminate the problem.

    Hope this helps.
     
  9. lc1996

    lc1996

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    First of all, thanks for the welcome and advice Safado & Robbie.

    Yes I did install the kit along w/ help from a couple of buddies. I do have Slee's adjustable upper control arms and they are adj. to the shortest length which I believe is only about a 1/2" shorter than stock. I thought you are suppose to shorten the arm instead to minimize the vibration/noise? I checked the Uj's at the time and they are good, but will check them again tomorrow. Safado, I read that thread and this just confirms the conversation I had with Ben at Slee's about the rear drive shaft issue when lifting your rig. So looks like I'm gonna have to invest in a double cardan shaft soon since I don't want to reck havoc on the other components of the driveline. Otherwise, I could deal with the noise if that was the only issue.
     
  10. MTNRAT

    MTNRAT

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    I have the 6" lift and the installation of a double cardan rear driveshaft solved all vibration from the rear driveshaft.
    Cheers,
    Sean
     
  11. lc1996

    lc1996

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    Sean,
    With the double cardan installed do you have the upper control arms lenghten?

    Carl
     
  12. MTNRAT

    MTNRAT

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    I do have the adjustable upper control arms. You need them to get the pinion pointing directly at the transfer case. Here is a good explanation of driveline geometry. http://www.4xshaft.com/driveline101.html . I obtained all needed stuff from slee. They did need to be adjusted longer, IIRC.
    Cheers,
    Sean
     
  13. alia176

    alia176

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    Sorry, but I don't follow this logic... :D Is the pinion forced down or the is Tcase forced up? The pinion stays in the same angle in the rear, hence the bad angle :confused: