Rear end whine -
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Unread 04-24-2005, 06:57 PM   #1
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Rear end whine

Ok guys,

I'm not too active on this board, so I really appreciate anyone that helps someone like me that doesn't contribute much. My mom has a 99 JGC, 2WD, 4.0L. It has 80,000 miles on it.

Lately, my mother has been saying that a whirring noise is coming from the back of the Jeep. I realize that "my car is making a noise" is the hardest thing to diagnose over the internet, so I'll do my best to describe it.

Its definitely a noise that increases in pitch with velocity. You can only hear it when there is a torque on the driveshaft (i.e., when coasting, it goes away). Its loudest while accelerating (I've only heard it once, and I wasn't driving, otherwise I would have put various loads on it to see how it changed). If you throw the tranny in neutral, it goes away completely, so its not engine related.

The noise doesn't decrease in pitch once you shift, so I think its only dependant upon the angular velocity of the driveshaft, and not the transmission.

I change the diff fluid at 60,000 miles with 75W90 Synthetic Gear Oil. At the time, the old oil looked old, but nothing out of place. I checked the rear diff to see if perhaps the oil had leaked out, but the area was bone dry. I did not have time to climb under the car and actually check the diff oil level.

At 78,000 miles, I flushed and filled the trans and put a new trans filter on. After that I drove the car for about 3 days with no incident before I went back to school.

My guesses are either that there is something wrong with the differential, wheel bearings, halfshafts, or mabye the U-joints (I don't even know if the car has U-joints).

Oh, and the diff is just a regular open diff, no LSD.

Anyone that has any idea of what this noise might be, your experience is greatly appreciated. If I can give you any more information, just ask! Thanks alot guys!

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Unread 04-24-2005, 08:37 PM   #2
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It sounds like the rear end might be failing. Mine was doing the same thing and I had to have it rebuilt.
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Unread 04-24-2005, 10:02 PM   #3
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CK the diff, take the cover off, and have a look see? Pinion bearing can make that sound too......Let us know what you find out.
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Unread 04-25-2005, 08:23 AM   #4
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also check the carrier bearings for play. theyre notorious for going out.
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Unread 04-25-2005, 08:27 AM   #5
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Hi all

If the carrier bearings are out, is this a shim/preload adjustment, or does that mean they're shot and need replacement?
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Unread 04-25-2005, 08:37 AM   #6
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I'd replace them.

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Unread 04-25-2005, 09:26 AM   #7
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If you replace the carrier bearings, do you have to do the whole ring-pinion preload alignment thing?

Are there any particular symptoms of the carrier bearings going? Mine's making a sort of chuff-chuff but can't decide if its wheel bearings, carrier bearings or LSD clutches...

Its done 103K, so probably all 3!
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Unread 04-27-2005, 09:39 AM   #8
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Thanks everyone

Thanks for everyone's suggestions. I'll be taking a look at those bearings the next time I'm under the car. I think if anything I'll be going with a rebuild kit and just have it installed since I won't be around (I go to school pretty far away from where my parents live) to do it.

I think its pretty sad that differential bearings would go after 80,000 miles. My volvo has 190,000 on it, and my BMW has 145,000. I guess anything can fail at any time, but this is the first I've seen of something like this.

Thanks again for the help guys.
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