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  #1  
Old February 15th, 2012, 21:13
Dustys Dustys is offline
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LOUD Rear Vibration or Hum disappears with rear Drive shaft removed

I am trying to diagnose my vibration and hum in my XJ. First off its pretty violent.
The vibration really starts up around 60 indicated on the speedo and increases as speed does.

The vibration is not in the steering wheel but felt throughout the whole vehicle, panels shake and floor vibrates.
At certain speeds its waxes and wanes from loud to real loud. Its a very deep bass hum, so much so I can't hear the subwoofer bass.

This is a new jeep to me and has done this since I aquired it.

Heres what I've done so far to troubleshoot:

1: Since it felt like it was coming from the rear I first removed my rear driveshaft and drove at highway speed in 4wd with the front pulling me and BINGO no more vibration.

2: My pinion angle and driveshaft are near straight on with a degree or 2 down for torque. The rear of my transfer case is a double cardan.

3: All my tires are new and balanced size 35x12.50-15. Plus can't be that cause they don't vibrate with the rear shaft gone.

4: Haven't had my driveshaft balanced yet going to do that tomorrow hopefully.

5: Of course the vibration is worse on acceleration/under load but I still hear some while coasting, but none when the rear shaft is gone.

Solutions?

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  #2  
Old February 15th, 2012, 22:41
FloydXJ FloydXJ is offline
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Re: LOUD Rear Vibration or Hum disappears with rear Drive shaft removed

Sounds like the driveshaft may have one or more bad joints. Did you get a good look at the caps while it was out? The balancing should help, but they are rarely SO out of balance that it shakes as much as you describe. This could also be a pinion issue, but when you say the pinion and DS are straight, I assume that means the pinion is facing upward, aiming toward the t-case?
Laslty, it could be a gearing setup issue, as they can be a lot quieter when not under load.

But it sounds mostly like U-joints - make sure to check them out.
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  #3  
Old February 16th, 2012, 00:28
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thisissparta thisissparta is offline
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Re: LOUD Rear Vibration or Hum disappears with rear Drive shaft removed

if its not any of the u joints its probably the cardan joint its self
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  #4  
Old February 16th, 2012, 03:31
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KingIce KingIce is offline
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Re: LOUD Rear Vibration or Hum disappears with rear Drive shaft removed

You got a hack n' tap kit on your t-case? I had the same issue with my hack n' tap kit some time ago...drove me crazy, cause it was hard to figure out.
The problem was, that the fixed yoke wore out (<- is this spelled right??? ) because i cut the outputshaft too short. BUT i didn't realize that for a long time, because if you tried to check the yoke by hand it felt tight and didn't move. When i loosened the bolt that fixes the yoke on the shaft a little i could rattle the yoke around on the shaft. The force coming from the driveshaft should be enough to move it even with the bolt tightened.
I solved the problem by installing the Advanced Adapters SYE Kit. No more vibrations, no more ugly noise, and the certainty to have a really FIXED yoke.
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  #5  
Old February 16th, 2012, 09:17
Dustys Dustys is offline
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Re: LOUD Rear Vibration or Hum disappears with rear Drive shaft removed

I pulled the rear u-joint off, all the caps spin freely and weren't dirty I packed it with new grease anyway, all the needle bearing were in place. No slop there. This u-joint is new anyway, although I know they can still go bad.

When I had the driveshaft off the double cardan was very tight in the places it should be but moved freely on all axis of the ujoints, I pumped new grease into both of the CV ujoints on the shaft also. There is no play in the rear or front of this driveshaft. I can't budge the pinion shaft in either direction laterally either.

Floydargue- yea I mean the driveshaft and and pinion are angled toward the t-case.

Yes I do have a hack n tap not sure which on though.
It's not loose or anything
Here's some pics of my setup

<a href="http://www.flickr.com/photos/_fire/6887083657/" title="photo 1 by Agustus McCrae, on Flickr"><img src="http://farm8.staticflickr.com/7061/6887083657_104e334e9e_z.jpg" width="640" height="478" alt="photo 1"></a>

<a href="http://www.flickr.com/photos/_fire/6887083909/" title="photo 2 by Agustus McCrae, on Flickr"><img src="http://farm8.staticflickr.com/7069/6887083909_2e05d01495_z.jpg" width="640" height="478" alt="photo 2"></a>



I
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  #6  
Old February 16th, 2012, 09:20
Dustys Dustys is offline
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Re: LOUD Rear Vibration or Hum disappears with rear Drive shaft removed

Sorry new to this. Didn't see the photo link button

Hopefully Better links to the photos



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  #7  
Old February 16th, 2012, 11:53
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sidewaysstarion sidewaysstarion is offline
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Re: LOUD Rear Vibration or Hum disappears with rear Drive shaft removed

Quote:
Originally Posted by Dustys View Post
I pulled the rear u-joint off, all the caps spin freely and weren't dirty I packed it with new grease anyway, all the needle bearing were in place. No slop there. This u-joint is new anyway, although I know they can still go bad.

When I had the driveshaft off the double cardan was very tight in the places it should be but moved freely on all axis of the ujoints, I pumped new grease into both of the CV ujoints on the shaft also. There is no play in the rear or front of this driveshaft. I can't budge the pinion shaft in either direction laterally either.

Floydargue- yea I mean the driveshaft and and pinion are angled toward the t-case.

Yes I do have a hack n tap not sure which on though.
It's not loose or anything
Here's some pics of my setup







I

Fixed
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  #8  
Old February 16th, 2012, 12:47
98XJLongBuild 98XJLongBuild is offline
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Re: LOUD Rear Vibration or Hum disappears with rear Drive shaft removed

Popped off you diff. cover and stick a flat head under the carrier and see if there is any play in it,, either up and down or side to side. If so your carrier bearings are gone.
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  #9  
Old February 16th, 2012, 17:23
darksidemj darksidemj is offline
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Re: LOUD Rear Vibration or Hum disappears with rear Drive shaft removed

Since the noise is more noticeable under acceleration sounds like it may be pinion bearings. It's may be the shaft but sounds more like pinion bearings from the way you described it.
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  #10  
Old February 16th, 2012, 20:19
Dustys Dustys is offline
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Re: LOUD Rear Vibration or Hum disappears with rear Drive shaft removed

Took the driveshaft in to Inland truck today. The tech called me after 30 minutes and said the slip yoke on the shaft was toast. The holes in the yoke no longer hold the unjoint caps tight. And they spin also while in the yoke.

I feel stupid. I didn't notice slop in the u joint when installing. But thought "these sure are easier than my trucks u-joints to install, I don't even need my press"

The tech was convinced that's where my vibration was coming from.

We'll see

I get it back tomorrow afternoon.

Next ill try pulling the diff cover and seeing about those pinion bearings.
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  #11  
Old February 17th, 2012, 05:49
98XJLongBuild 98XJLongBuild is offline
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Re: LOUD Rear Vibration or Hum disappears with rear Drive shaft removed

If something in ur driveline has bad vibrations it most likely Will Get something else. So when you check ur pinion bearings look really close and try to pry it in any which way.
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  #12  
Old February 17th, 2012, 09:10
Dustys Dustys is offline
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Re: LOUD Rear Vibration or Hum disappears with rear Drive shaft removed

I agree with that. It also doesn't help the rear diff was only 1/3 full and the T-case was empty. I'll be lucky if I dont have major damage. I should have checked those things before buying but the rest was clean and the fluids that have sticks looked good. So in doing my post buy run through I've found a lot left to be desired.
Still got it at a decent price although it be nice to have a little money back considering the risk after not having fluids in critical components.

But hell will freeze over before I get any money back.
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  #13  
Old February 17th, 2012, 21:42
xjbubba xjbubba is offline
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Re: LOUD Rear Vibration or Hum disappears with rear Drive shaft removed

Quote:
Originally Posted by Dustys View Post
"---

But hell will freeze over before I get any money back.
"Buyer beware" is the general legal rule--"sold as is" is presumed when buying a used vehicle from an individual, in most states.
Hopefully you will solve your vibration problem, and update this thread for others to learn from.
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  #14  
Old February 18th, 2012, 23:31
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98REDXJ2 98REDXJ2 is offline
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Re: LOUD Rear Vibration or Hum disappears with rear Drive shaft removed

uhhhh i got a 98 xj 3days ago and it has a rear hum, sounds like the rear axle, its only when driving over about 25mph though.... suggestions?
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  #15  
Old February 19th, 2012, 06:47
98XJLongBuild 98XJLongBuild is offline
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Re: LOUD Rear Vibration or Hum disappears with rear Drive shaft removed

Quote:
Originally Posted by 98REDXJ2 View Post
uhhhh i got a 98 xj 3days ago and it has a rear hum, sounds like the rear axle, its only when driving over about 25mph though.... suggestions?
You'll need to do all the same things as the PO.

Start to make Sure all fluids are top off with the correct fluid. Check all your ujoint for the driveline and for the front axle shafts. Then check you ring and pinion for any slop.

After those minor checks then we might be able to pin point the issue a little better
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