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-   -   Rear End Noise - 2006 325xi (http://www.unitedbimmer.com/forums/showthread.php?t=16552)

Ebby1600 09-27-2009 06:17 PM

Rear End Noise - 2006 325xi
I looked over the threads in this forum and didn't see anything like what I am experiencing with my car. Soooo...here is what I observe and what I am doing about it.

I purchased the car used with 16000 miles. Certified BMW. After 5k or so highway miles I noticed a pulstating noise while driving which seemed to come from underneath the vehicle. I checked the runflats with my son who is a mechanic and he noticed scalloping on the outside edge of the tires. I read up on this an others have had a similar problem. So I decided to purchase a new set of tires (not runflats) and have them mounted and balanced. I thought the problem was corrected but recently I noticed rhythmic pulsating noise again. This noise is different from before. I checked the tire pressure and wear after 12000 miles and the tires look great (Kumho Ecstas). I don't believe the noise is tire noise.

To test my theory I took the car up to the high school parking lot and made a series of slow (10 mph) tight turns in the left and right hand directions. While turning left I hear a distinct rhythmic groaning/grating noise. While traveling straight, starting at about 20 mph I heard the same noise. Not so much when turning to the right. The noise is coming from the rear of the car and I'm leaning towards a bearing or CV joint that is or has gone bad. What are the collective thoughts of this forum?

Thanks for listening.

3050rpm 09-27-2009 07:17 PM

It could be a rear wheel bearing, mine gave up the ghost last year, but that's after 13 years of ownership. For one to go on a three year old car seems quite unlikely. As you have an "x", I wonder if there's something with the driveline. Do you recall having bottoming out at any time? Also, just to add to your anxiety, "certified" can be a meaningless term concerning used cars, any type, but before worrying about that, getting a diagnosis is in order.

Ebby1600 09-27-2009 08:57 PM

Appointment made with service
I don't recall bottoming out but at some point in the past three years I possibly could have but don't remember. Do you have another theory? I would be surprised too if it was a bearing. I did read at another BMW list about an M5 that was making noise in the rear and the service department ended up putting a different type of fluid in the differential. It really has me baffled because when I drove the 2007 I really felt like I was in a luxury car. In mine it sounds like there is a hole in the floor letting road noise into the cab. Sure hope the dealership can sort this out.

If it is drive train I'm still covered by the warranty. Thanks for listening.

3050rpm 09-28-2009 03:02 PM

The reason why I asked if you had bottomed out at some time (pot hole, road hazard, whatever) is to suggest that the driveshaft may be out of alignment, although this seems remote. Similarly, I was going to suggest that a rim could have gotten dented, but as you recently put on new tires, I should think they would have caught something like that, though not necessarily.

I think I came across somewhere that "M" cars do take a different differential fluid, but why that should apply to a non-M doesn't make sense to me. But that does raise a question, any fluid leaks in the rear end, or elsewhere? Torn half shaft boots?

By the way, is this an automatic or a manual?

Big Evil 09-28-2009 05:01 PM

In addition, you don't get a groan or a click noise happening do you? If so there was a service action having to do with the rear sub frame, dealer should be checking that out.

Ebby1600 09-28-2009 07:25 PM

I have an appointment with the dealership to diagnose the situation. In dealing with this noise one of the difficulties I have had is in describing the noise. A groan? I guess it could be described that way. Another way is to imagine a croaking bullfrog caught under the car and each time the axle makes a rotation a muffled 'croak' come from under the car.

I did hear about a service bulletin regarding a rear end problem. Does anyone know the number of that bulletin? I downloaded the pdf list and bookmarked the site to read them.

I am really anxious to have this sound go away and return to quiet motoring.

PS - After writing about the M5 diff oil I realized that I am comparing apples to oranges and the M5 anecdote most likely does not apply to my situation.

3050rpm 09-29-2009 01:54 PM

Further thoughts, some perhaps a bit farfetched... Maybe the differential oil could stand to be changed; and might it be the exhaust, either it's on the way out, or a hanger may have come undone so it's knocking against something? Trying the simpler possible explanations first...

Big Evil 09-29-2009 09:23 PM

Not positive on the action number for the rear end noise. The dealer however should be well aware of it, I think it was sent out to them around 3 months ago. And they should also do as 3050 suggests and look for the obvious easy stuff while its up in the air.

Ebby1600 12-05-2009 11:44 AM

Recap: I was hearing a thump thump thump noise at low speeds and while making turns to the left and right. At higher speeds the thumping frequency increased until it was a definite whirring noise which made talking and listening to the radio difficult. This forum made some suggestions and I set up an appointment with my BMW dealer.

Ok I had the car seviced and thank goodness I wasn't crazy. The car was making an awful noise from the rear end and yes the dealership heard it too! The problem was, in fact, a bad wheel bearing. They also noticed a click in the steering column when turning the wheel which was listed in a service bulletin I believe. All in all a successful solution to the problem. Now the car runs as quiet as the day I purchased it and the joy has returned to my life. Thanks for the suggestions and hopefully I will enjoy thousands of miles of driving pleasure.

3050rpm 12-07-2009 04:03 PM

:thumbup Was the bearing covered under warranty?

Ebby1600 12-07-2009 08:56 PM

Rear End Noise Repaired by Dealership

Originally Posted by 3050rpm (Post 171012)
:thumbup Was the bearing covered under warranty?

The whole thing was covered under my Certified BMW warranty. I had to pay a deductible which amounted to $45.00

3050rpm 12-07-2009 11:37 PM


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