Vibration

Discussion in 'Flat Fender Tech' started by jackdog, Jul 18, 2016.

  1. Jul 18, 2016
    jackdog

    jackdog Member

    Finger Lakes NY
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    Got my CJ3A build on the road but it has a vibration starting at 30mph. The front hubs are unlocked and the Tcase is in 2 high. If I push in the clutch it goes away and if I shift to neutral with the clutch out it's gone. It has all new u-joints and the D44 rear was gone thru and looked good. The Tcase is a D20 mounted to the T14.
     
  2. Jul 18, 2016
    ITLKSEZ

    ITLKSEZ Volvophilic

    Post Falls, ID
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    -What are your driveshaft angles like with the D20?
    -And are they the same at the t-case/shaft and shaft/pinion?
    -Did you have your driveshaft apart at the splines, where you could have gotten it back together out of phase?
    -How is the condition of the splines? Any side-to-side slop?

    It sounds like a classic driveshaft vibration from here; you just have to pinpoint the issue.
     
  3. Jul 18, 2016
    ITLKSEZ

    ITLKSEZ Volvophilic

    Post Falls, ID
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    Also, is it worse under acceleration, deceleration, or the same?

    Did you have it running with the D20 before?
     
  4. Jul 18, 2016
    jackdog

    jackdog Member

    Finger Lakes NY
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  5. Jul 18, 2016
    jackdog

    jackdog Member

    Finger Lakes NY
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    Here is photos of the driveshaft angles. It came from a 74 CJ5 as did the whole running gear, The splines felt tight and all I did was replace the U joints. I did reweld the spring pads on the axle for a better angle.
     
  6. Jul 18, 2016
    ITLKSEZ

    ITLKSEZ Volvophilic

    Post Falls, ID
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    Bingo. Without a double cardan joint up at the T-case, pointing the pinion up towards the T-case will give you a vibration. With standard joints, both should be at the same angle.

    Torsional vibrations occur twice every time the driveshaft rotates. If both joints are at the same angle and in phase, they essentially cancel each other's vibration. By removing the angle of one, you removed the one's vibration, and now you are feeling the other's.

    You can either weld your pads back where they were, or call Tom Woods for a new shaft with a double cardan. It'll run you around $390.
     
  7. Jul 18, 2016
    Alan28

    Alan28 Sponsor Sponsor

    Ch√Ętillon en...
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    there are top pros on Early cj5!
     
  8. Jul 18, 2016
    ITLKSEZ

    ITLKSEZ Volvophilic

    Post Falls, ID
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    I should add that putting your spring perches back down where they were might not get rid of the vibration totally, but it will help. U joint life could be shorter too.

    The new drive shaft should fix the vibration for good and will have adequate joint life.
     
  9. Jul 18, 2016
    Oldriginal86

    Oldriginal86 Member

    Pasadena, Md.
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    You could try shimming the pinion back down to the angle of the transfer case. If that eliminates the vibration then cut off the pads and re-weld. Personally I would try that first before buying a new shaft, but I'm cheap.
     
  10. Jul 19, 2016
    jackdog

    jackdog Member

    Finger Lakes NY
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    THANKS! Got a set of shims I can throw in to see if it makes a difference. If not guess I will get a new shaft. Will post results.
     
  11. Jul 20, 2016
    47v6

    47v6 junk wrecker! Sponsor

    Washington DC.
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    I was very happy with the Tom Woods driveshaft I got from him.
     
  12. Jul 20, 2016
    jackdog

    jackdog Member

    Finger Lakes NY
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    Placed some shims in today. Did not get rid of the vibration but it changed and it became less. Must be on the right track.
     
    ITLKSEZ likes this.
  13. Jul 20, 2016
    Oldriginal86

    Oldriginal86 Member

    Pasadena, Md.
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    Did it bring the pinion angle up to match the down angle on the output yoke?
     
  14. Jul 20, 2016
    45es

    45es Sponsor Sponsor

    Naches, WA
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    I get the sense even though you are following the suggestions of the members here, you are still guessing as to how much adjustment is needed and/or if a new driveshaft is needed. I suggest you read the link at Pirate4x4 regarding driveshaft geometry and take as much guess work out of the process as you possibly can.

    Pirate4x4.Com - Extreme Four Wheel Drive
     
  15. Jul 20, 2016
    tarry99

    tarry99 Member Sponsor

    Northern California
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    The first thing I would do is get your drive-shaft re-balanced...........all that under body sealer & paint you have sprayed on it is more than enough in weight to throw it out of balance.
     

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