Constant humming from rear on or off powerin

[stuart911]

Hi, I know there are topics out there around rear diff/bearing/prop noise but none of them describe my problem exactly. The noise is not a whine, it is a hum or a drone would better describe it and it's constant, on or off the power. It gets louder with speed but it never goes away at any speed. There's no vibration through the car, changing direction, braking, driving style make no difference, it is there all the time. Z4 3.0si coupe 2006 61K miles. Is it the diff, wheel bearing or central prop bearing? And how can I check for sure, up on a lift, run the car and put a screwdriver and my ear against each? Thanks for your feedback

 

[paulgs1000]

I had this noise on my 2.0 litre - it sounds nothing like a wheel bearing and like you I thought it would be something else. Take it to a specialist independent (as I did) and they will let you know - Mine was a wheel bearing but as I said I thought it would be a diff problem or prop shaft - allsorts . . . never thought it would be a wheel bearing with such a noise - but it was.

Check out the previous post about such noise - just commented on it and that was a wheel bearing.

Good luck and I hope you get it sorted soon.

 

[mr nurburgring]

What tyres you running on the rear?

 

[patriot66]

Mine used to make a similar noise. Changed the Bridgestone Run flats to regular Avon ZZ5 tyres and hey presto....no noise!

 

[stuart911]

Thanks for all you comments. Could it really be just tyres? Hope so. Cos I'm running run flat Pirellis on the rears, Bridgestone on the front. I was going to change them to non-RFTs to improve the ride and tramlining so sounds like I should do that before anything else and see. Thanks a lot. I'll report back when done

 

[mr nurburgring]

I have had the very same noise, usually with cheap or oddly worn tyres, I didn't believe it at first until I borrowed a mates wheels of his 3 series and went for a drive. No noise at all!
I have used run flat and non run flat tyres, I don't think it due the the structure of the tyre more the way the tread makes contact with the road.