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Vibration

Discussion in '40- & 55-Series Tech' started by folsom50, Dec 31, 2003.

  1. folsom50

    folsom50

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    My driveline has a vibration, enough so that if I rest my hand on the shifter going down the road it goes numb. It's high frequency. There's also a cyclical growl coming from the rearend at hiway speeds but it don't seem to match the shifter as far I as I can tell. I took the driveshaft off and the u-joints are nice and tight and other than the smallest amount of radial play, the slip yoke is tight. U-joints are in time. So, do I need to pull the third member and have it rebuilt? or is everything I just described considered "normal" for a fj-40?
     
  2. fjcruiser

    fjcruiser

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    I would check your pinion angle first. If you have a lift or ext. shackles, you should install caster shims to tip your pinion back down.
     
  3. folsom50

    folsom50

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    Just did that a couple days ago, 4 deg. didn't do anything for the rearend, but wow, what a difference it made with steering on the highway! Oh, just incase I screwed up, on the rear the shims should be thick part forward to actually tip your pinion up...correct?
     
  4. fjcruiser

    fjcruiser

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    I forgot to add... Drain the oil in the rear end and look for chunks. I had to replace the 3rd member in my rig due to metal in my oil.
     
  5. fjcruiser

    fjcruiser

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    No, IIRC the fat part should be back so that it tips the pinion down. You want the pinion and the transfer case output to be parallel.
     
  6. cruiser_guy

    cruiser_guy

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    I had a growl from my rear end. It turned out that the bearing retainers had spun. I ended up getting a replacement 3rd member.
     
  7. folsom50

    folsom50

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    If the pinion is supposed to be level with the t-case, then I'm way off...don't make much sense, at least in my little brain. I really wonder if there's something way out of quilter in my third member.
     
  8. CruisinGA

    CruisinGA

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    The pinion should only be pointed at the rear of the T-case when using a double-cardan CV shaft. Which I assume you are not.
    As fjcruiser said, with normal d-shafts the pinion should be parallel with the rear output of the t-case. It has to do with funky driveline shiz. This could very well be your problem.
     
  9. hammerhead

    hammerhead

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    Bailey is right. Get the pinion angle right before messing with third member. It only takes a few degrees to make it vibrate. Correcting the pinion angle is a lot cheaper than dealing with your third member.
     
  10. folsom50

    folsom50

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    I'll flip the shims today and see what happens
     
  11. CruisinGA

    CruisinGA

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    Depending on your lift springs/shackle combo, 4 degrees may be too much. Be sure to visually check it all out as well.
    I needed 2.5 degree in the front only with skyjacker springs and stock length shackles.
     
  12. folsom50

    folsom50

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    I haven't figured out exactly how much lift I do have, the springs are after market and the shackles are 5 1/4" between bolt centers. I do know that even before I tipped the pinion up with the shims that it was already tipped up quite a bit.
     
  13. folsom50

    folsom50

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    Flipped the shims and it got rid of the vib. in the shifter, but the growl is still there. I'll just live with it for the time being until I can get the third member rebuilt. Oh, checked the plug and found no metal chips in the gear lube.
     
  14. TJDIV

    TJDIV Back in The U.P.

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    I had the same problem. I had to shim the rear end, but then I had to also space my t-case down a bit to meet the angle. .... I will say this....it's amazing how little things can be off, and how big the problem can be.

    Good Luck.

    IV
     
  15. TJDIV

    TJDIV Back in The U.P.

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    OH...almost forgot to mention. Had to correct PO's position of the 350. Had to move it TWICE. ahhhhhhhhhhhfizuck.....
     
  16. 78crzr

    78crzr

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    If I've got a 4" Skyjacker lift with stock length shackles, do I need to shim and how much? Front & rear?
     
  17. CruisinGA

    CruisinGA

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    2.5 in the front.
    I don't have any in the rear, I may put a 1.5 or 2 on the rear when I get a chance, to see if it helps, I don't get any vibration until I exceed 67 mph.
    Don't forget to get new spring pins, and space the head up with some pipe so that it still protrudes into the spring plate on the axle.