Loud whine / howl from rear - diff ?

[jnwright71]

All, help please ...

My Z4 2.5si manual has been sat for 4-5 weeks unused. Took it out today and experienced a loud whine / howl from the rear of the car when off load at various speeds (it didn't do this before). When I re-applied the accelerator, the noise disappeared. When the car was warmed up, the noise was greatly reduced.

I am no expert, but this seems to be either:

- rear wheel bearings (no sign of issues when checked for play)
- rear diff (common noise, worn bearings, loose preload bearing etc)

I have read lots of advice online about changing the oil for either:

- Amsoil 75-90w (svg) EP
- Amsoil 75-140w
- Redline 75-90w
- Redline 75-140w
- BMW oil with friction modifier additive
- include a PTFE or similar friction reducing additive

Has anyone else had loud diff (or rear noise) and if so, any advice on how you overcame it would be great.


Many thank, James

 

[Stuart Truman]

Or possibly a binding handbrake after over a month being applied?

 

[jnwright71]

Have moved it in and out of the garage a number of times during that 4-5 weeks and don't always leave the handbrake on when in the garage, so this is unlikely, but I will check. Definitely very loud and diff type noise ...

Thanks, James

 

[jamiez]

Does it occur after a certain speed or noticeable more after a certain speed?

 

[jnwright71]

Hi,

It seems to occur throughout the speed range, but predominantly when the engine / transmission is off load or under very light load, pressing the accelerator again clears the issue.

Thanks, James

 

[Adamski]

No sign of fluid leak from the diff area? Sounds diff related


Sent from my iPhone using Tapatalk

 

[jnwright71]

No signs of any leaks. I haven't had the car that long, it has a main dealer history and has never been checked for a similar noise. Could it be wheel bearings after all ? (I would have through this would be more of a rumble and more continuous rather than load related).

Thanks, James

 

[Gyro433]

Is this the same noise as in this tread. Listen to the video from the OP.

Gyro

http://www.z4-forum.com/forum/viewtopic.php?f=3&t=64342

 

[jnwright71]

I cannot really tell from that video, but mine is really loud, almost like a jet engine spooling or turbo overboosting. A mechanic friend has suggested this could be brake pads breaking down ...

All advice / ideas welcome. Thanks, James

 

[jnwright71]

Bizarre ....

This is now completely sorted. I took the Z4 to a friends last night and the noise gradually reduced as I was driving the circa 5 miles (a couple of gentle pulls on the handbrake included to clean the drums / shoes). We put the car up on his 4 poster ramp to check the diff etc but no signs of leaks / grinding. We then checked the rear brakes and bearings and all OK. Finding no issues at all, I took the car for a 20 mile run and there was not one squeak, whine, clunk or rattle - the noise has totally disappeared !!

I can only assume that the car was in desperate need of a good run and this freed up anything that was slightly sticking - cheapest repair ever !!

Thanks for all the advice.

James