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  #1  
Old 07-03-2012, 10:59 AM
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Rear moaning over 55mph

WK HEMI 2006
I have noticed that in the speed range 50<>80 mph a constant "moan" is audible ("wuuuuuuuuuu") , it disappears, all of a sudden, when NOT accelerating.

Kinda of video I have made here http://youtu.be/Ouorxy1rIwg
90000Km "mileage"

Any idea?
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Old 07-03-2012, 12:15 PM
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Re: Rear moaning over 55mph

I'd start by checking fluid quality and fill level on both front and rear diffs.

When was the last time they were serviced?

It sounds like typical differential whine - if it is when coasting and not accelerating it usually indicates worn pinion bearing...you may also get lucky and it is just the bearing preload that has loosened. However, since it is there only when accelerating I don't think you're that lucky!

Is there any difference in the sound when turning left or right? If so, I would suspect wheel bearings, but to me at least, it sounds like a differential issue (especially with the 'on' 'off' pattern that fluctuates with loading and unloading the diffs).
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Old 07-03-2012, 05:52 PM
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Re: Rear moaning over 55mph

Sounds like a differential. Drain the fluid and do a service remember to add the limited slip fluid if necessary
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Old 07-04-2012, 07:25 AM
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Re: Rear moaning over 55mph

The man at the service had a road test and stated that the problem lies in the rear pinion gear... could it be?
New video here: http://goo.gl/VBmKd
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Old 07-04-2012, 08:35 AM
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Re: Rear moaning over 55mph

Quote:
Originally Posted by Blutarsky View Post
The man at the service had a road test and stated that the problem lies in the rear pinion gear... could it be?
New video here: http://goo.gl/VBmKd
Yes. As stated previously, if the noise isn't affected by turning (indicating a wheel bearing), and fluid quality/quantity is good, the rear pinion is a probable cause.

It's a fairly common problem. Some people choose to live with the noise - it could go another 50,000 miles like that, or it could break down at the end of the street.
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Old 07-04-2012, 08:40 AM
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Re: Rear moaning over 55mph

The service quoted some 800$ for the spare parts (new pinions and bearings) and 1200$ for the service.
Maybe I could look for the spare parts in the states and find a cheaper service.
Is it a sort of difficult replacement or will an average service could do the task?

What path would you follow? The chief at service admitted he wouldn't touch the car...
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Old 07-05-2012, 11:31 AM
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Re: Rear moaning over 55mph

I just had to get my rear pinoin seal replaced about 2 months ago. I had the whiiiir whine under accel and when I did my rear brake job, I noticed that there was a rotational pattern of oil under the Jeep in front of the differential. The leak wasn't bad, but I decided to get it replaced anyways. Cost me $300 at the local stealer including a rear diff flush at the same time.

The new seal cured the whining noise. Now to fix my clunky transmission...
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Old 07-05-2012, 11:48 AM
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Re: Rear moaning over 55mph

Did you check out my video?

http://goo.gl/3y5KU

Does it sounds like yours?
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Old 07-05-2012, 11:50 AM
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Re: Rear moaning over 55mph

Quote:
Originally Posted by Blutarsky View Post
Did you check out my video?
Does it sounds like yours?
Sorry at work and all sound is disabled on these boxes. I'll try to check it out when I get home if I remember.
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Old 07-05-2012, 11:51 AM
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Re: Rear moaning over 55mph

I would appreciate that
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Old 07-06-2012, 12:16 AM
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Re: Rear moaning over 55mph

Sounds like the noise I had. Every Jeep I've ever owned has had that sound so I thought it was normal. Once I replaced the pinion seal [due to the leak], it was just an added bonus that the cabin is extra quiet now.
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Old 07-06-2012, 12:19 AM
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Re: Rear moaning over 55mph

Thanks brent for checking out the video. I spent a few minutues on youtube looking at pinion seal's videos... it looks like it is plastic made... am I wrong?
If not, how can a plastic ring (pinion seal) affect the noise?
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