Baffling rear noise, 540

[jofusfarr]

I have a baffling noise in the rear of my 540i.

It's rotational, whirring, rubbing sound similar to a warped rotor. It changes with vehicle speed and appears on both sides or center of the car while driving.

I jacked the rear up, removed tires/wheels, and let her idle in drive. There is slight noise from both rotors with calipers removed, but it seems so quiet I'm not confident I've pinpointed it to there.


Could it be something else? Perhaps by removing the load from the suspension components I have masked it?

[Tiger]

I would say it is more likely it is your tire that is making the noise. What is the brand and model? How much tread left?

[Barney Paull-Edwards]

To give yourself a better chance, try putting axle stands under the trailing arms to get the shafts at roughly the same angle.also wind off the handbrake shoe adjustment wheel by wheel, which I suspect is the problem.

[jofusfarr]

While the parking brake was making noise, it was not the culprit.

The noise isn't really audible until around 20MPH, so I'll jack it up and test it again at 20+ MPH.

I'm also going to swap rear and front tires (they look fine however), lots of tread left and no signs of uneven wear. They are Yokohama, not sure of the specifc model.

I recently replaced motor/tranny mounts that was horribly disfigured - perhaps the driveshaft support bearing, or u-joint? Differential?

[bimmo_2007]

I recently replaced motor/tranny mounts that was horribly disfigured

I think it is the center mount some times it causes such a noises.

[jofusfarr]

I have isolated the noise to the driveshaft.

Raising the car again and clamping the throttle to around 40 MPH revealed a pronouced vibration along with the target noise.

Anything that might distinguish if it is the u-joint or the carrier bearing prior to removing the exhaust/heatshields to reveal the shaft?

[bimmo_2007]

I have isolated the noise to the driveshaft.

Raising the car again and clamping the throttle to around 40 MPH revealed a pronouced vibration along with the target noise.

Anything that might distinguish if it is the u-joint or the carrier bearing prior to removing the exhaust/heatshields to reveal the shaft?


I'd say it is the carrier bearing, same thing happened to me year ago with a Mercedes right after I changed the Tranny & Engine mounts.

[jofusfarr]

Finally discovered the source of the noise: left rear wheel bearing.

I had initially ruled this out due to the rubbing sound, unlike the typical whine of bearing failure. Furthermore, the resonation of the sound through the underside made isolating the source difficult (especially while running the car, with added exhaust noise).

The carrier bearing has no signs of failure - suprising considering how malformed the engine/tranny mounts were. I made replace this for good measure, however.