Z4 High Pitched Noise

[namnep]

Hi, first time forum post for me.
I have a 2005 Z4 3.0 Manual Convertible. 86000 miles. It has fault which is driving me crazy! It has a whine from which I'm certain is the rear end. My initial thoughts were that there was something caught in one of the brakes as I had the brakes renewed all round. Not so.
Is it wind noise? No
A BMW specialist had it for a while and said that although it was a much higher pitched noise that you would expect, it was a Diff noise.
New (used) Diff fitted, noise still there.
Is it wheel bearing? Although I have not replaced the wheel bearings I have done the normal wheel bearing check, i.e. Driving at various speeds at up to full lock in both directions and there is absolutely no difference in the noise which would therefore point away from wheel bearing.
Now here is the sickener. Its NOT there all of the time! When it comes on it is at exactly 21 Miles per hour and it goes off at 14miles an hour.
You can drive it for an hour and its not there and suddenly it comes on. The whining noise increases with road speed as a Diff noise would but much higher pitch.
When it is apparent you can knock it out of gear, switch off engine and free wheel and the noise is there.
Any ideas most gratefully welcomed.
David

[Needanothercoupe]

Hi, first time forum post for me.
I have a 2005 Z4 3.0 Manual Convertible. 86000 miles. It has fault which is driving me crazy! It has a whine from which I'm certain is the rear end. My initial thoughts were that there was something caught in one of the brakes as I had the brakes renewed all round. Not so.
Is it wind noise? No
A BMW specialist had it for a while and said that although it was a much higher pitched noise that you would expect, it was a Diff noise.
New (used) Diff fitted, noise still there.
Is it wheel bearing? Although I have not replaced the wheel bearings I have done the normal wheel bearing check, i.e. Driving at various speeds at up to full lock in both directions and there is absolutely no difference in the noise which would therefore point away from wheel bearing.
Now here is the sickener. Its NOT there all of the time! When it comes on it is at exactly 21 Miles per hour and it goes off at 14miles an hour.
You can drive it for an hour and its not there and suddenly it comes on. The whining noise increases with road speed as a Diff noise would but much higher pitch.
When it is apparent you can knock it out of gear, switch off engine and free wheel and the noise is there.
Any ideas most gratefully welcomed.
David

feel for you David, I had similar on an old Audi it drove me mad, it also used to start when I ever so slightly turned the wheel at speed, it would just start and then stop at a certain speed unfortunately I sold the car so never found out what it was but it was absolutely infuriating and frustrating, it was mentioned could be gearbox related but why would a slight turn to the left on the wheel trigger it?

[firebobby]

Nothing loose under the car ?, check the rear springs are not broken...could be resonating ?
Where are you, a photo of your car may help too, we may spot something

[PDJ]

Does this happen both with your wife in the car and without your wife in the car could be the wining noise.....

Centre prop shaft bearing?

[patriot66]

Tyres ? Swap wheels side to side or front to rear...it won't matter that they're staggered for a short 5 minute run whilst you ascertain if the noise has gone. I've had this previously on my Zed and other BMWs (all on the rear) that when the tread wears down to a certain level and you're at a certain speed on a certain kind of tarmac it sets up some kind of harmonic in the tyre carcass that can be heard in the car

[ph001]

Can you do a video, host on YouTube

[WillieK]

Came across this post multiple times. Had a high pitch noise coming from the rear passenger wheel that sounded almost like a loud mosquito from 25 mph to about 45 mph. Noise was absolutely annoying and well heard with the top or windows down. After taking it to multiple places I was told it was the tire, wheel, fuel pump, brakes, and then finally after a mechanic put on some chassis ears to narrow it down and start somewhere it ended up being the wheel bearing. Most techs agreed that they have never heard a wheel bearing make the sound. Thought I would post this for someone that comes across a similar issue.

[djean1981]

Had a similar high pitch noise in the back passenger side. It would start between 10 and 20 mph. It was the wheel bearing..

[djean1981]

Had a similar high pitch noise in the back passenger side. It would start between 10 and 20 mph. It was the wheel bearing..