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Rear moaning over 55mph

6K views 27 replies 8 participants last post by  Blutarsky 
#1 ·
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?
 
#2 · (Edited)
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).
 
#5 · (Edited)
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.
 
#6 ·
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...
 
#24 ·
I had the dealer do this around 30k and the problem persists. I wouldn't waste your money. Sounds like their default course of action.
 
#7 ·
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...
 
#9 ·
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.
 
#11 ·
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.
 
#13 ·
I wish I could help out on that one but I didn't do the replacement myself on this one for once. I glanced at the manual and it called for like 300 ft/lb of torque underneath the Jeep and frankly I couldn't do that without an overhead lift so I took it to the stealer. Honestly, the noise could have went away from something else they did with the rear diff at the same time.

All I know is after they did the rear flush/new pinion seal, if the noise is there, it's damn near inaudible. There's a road on the way to work that has a 55mph speed limit. I'll turn off the radio when I drive in in the morning and let you know if I hear it at all.
 
#15 ·
Well I listened this morning. The whine is still there, although much less pronounced. I'm unsure that any of my recording equipment could pick it up for a video. Just chalk it up to the standard Jeep rear diff whine lol.

All that being said, it's still my firm opinion that between the flush and new seal, the noise is definitely less audible.
 
#16 ·
The whine could have been reduced for a couple of reasons that I can think of after the rear pinion seal is replaced:

1) The diff was low on fluid because of the leak, and was topped up after the seal was replaced

2) The torque on the pinion nut was incorrect, and when they replaced the seal and re-torqued they used the correct value.

Just a couple of things I could think of...
 
#17 ·
The whine could have been reduced for a couple of reasons that I can think of after the rear pinion seal is replaced:

1) The diff was low on fluid because of the leak, and was topped up after the seal was replaced

2) The torque on the pinion nut was incorrect, and when they replaced the seal and re-torqued they used the correct value.

Just a couple of things I could think of...
I had considered that first option as a possibility, but as soon as I noticed that leak, I pulled off the cap and stuck my finger in the diff. There was still plenty of fluid (the leak must have been small, but looked larger due to the rotary spray pattern).

For option 2, knowing the shoddy work Jeep has been releasing lately, it wouldn't surpirse me if that was indeed the case.
 
#18 ·
From my experience (and I've replaced the pinion seal 3 times on my rig), the diff fluid always looks like a way worse leak than it actually is...a little certainly goes a long way when it is splattered all over your under carriage.

As to the tightening of the pinion nut, a lot of places will not do this properly - they are really supposed to measure the torque it takes to rotate the pinion flange, without the rear calipers or rotors on the axle to make sure when they tighten the new pinion nut and washer they get the bearing preload correct. From what I have seen, only one place actually went through the hassle of removing the rotors and calipers. The rest either just measured the rotating torque, or applied the 210 ft. lbs. to the pinion nut and hoped for the best...which can be asking for trouble down the road.

So long explanation short, it certainly wouldn't surprise me if at some point the pinion seal nut either loosened or had the wrong torque applied to it.
 
#19 ·
I was experiencing something similar to the whine you're hearing in the videos. I had a 2004 Ford Exploder and the rear end whine was ridiculously loud. The first thing I did was replace the fluid with a thicker gear lube along with the LS additive. When that didn't solve the problem I had my local shop look at the rear and they said the rear pinion gear was worn and pitted. This work was done at ~94,000 miles in 2010 and it cut down on the noise tremendously. I'm sure I could have kept the truck as it was but I just couldn't take the noise. A lot of people on the Ford forums fixed their rears by just turning the radio up.
 
#20 ·
facts:
- the oil has been replaced 6 months ago
- the oil has been checked yesterday and the level is perfect
- the pinion has never been touched/fixed... no change on original torque

The only thought is that the pinion gear may be worn.... unfortunatelly :-(
 
#22 ·
I've been told the whining on my WK is the U-Joints on the driveline. I get the clunks/ticks semi-hard acceleration along with the whining around 45 mph.
 
#28 ·
I mean they may have designed the pinon in such a way it is noisy, or they may have used a poor quality alloy that gets worn and noisy after a while.

This WE I drove for 500Km, gets really annoying, particularly for people sitting in the rear of the car.

2000$ to get it quiet again is very bothering too!
 
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