Help: How do you identify the howling of the diff or the wheel bearings?

[///WeissM]

I have a howling (only when rolling) from the rear of the car. I need to know is it from the wheel bearings or the diff. Car had 200K. Thanks.

[Mclassy]

Does it get louder under acceleration?

[///WeissM]

Yes, but not high pitch.

[z31maniac]

Are you sure its not the CSB?

[Mclassy]

Yes, but not high pitch.

Well, I know when my A4 bearings were going, they made a low howling and got louder (no pitch change) as I accelerated. I have a hard time thinking it would be your diff. Ive never heard of differentials howling. Do you know if the wheel hearings were ever changed?

[E30_fiend]

Its definitely the wheel bearings. The diff makes a high pitch whine. The wheel bearings sound like it is echoing inside the car. Don't take a chance just changing one. Do both, they are like 30 or 40 bucks a piece. The diff will also whine at a roll. The wheel bearings make a woosh woosh woosh noise when they are bad.


E30_Fiend

[Julien]

does it change depending on what direction you turn? if not.. probably your diff input bearing..

[E30ownerwithanopinion]

do you hear it when you are in reverse?

[///WeissM]

You had an A4 too? :) I used to had one as well. I just acquired this cab not long ago. No history. The shocks/struts was completely shot (just replaced with Bilstein Sport & H&R Sport last week, so happy) so I imagine the bearing never been change with 200k on the clock. Now if I can get this noise go away I will be a very happy man.

[///WeissM]

do you hear it when you are in reverse?

Hmm, I need to see if I have the same noise in reverse or not.

[E30ownerwithanopinion]

try in reverse on all three of the following... up hill, flat road, and down hill.

[Mclassy]

Well wheels bearings usually make noise at certain speed, so I guess you could justify that if you dont reach that speed. I still think you should be able to tell the difference. From what I know diffs usually click/clunk when they are having problems.

[emi325i]

Could be the tires.. poor alignment will quickly get your tires to sound something like: wowowowow

[Mclassy]

Could be the tires.. poor alignment will quickly get your tires to sound something like: wowowowow

Yes it could be bad alignment too, but they dont howl like a wheel bearing. Like someone stated about if you have the angle of the wheels (left or right) and you notice it stop and start again then you can determine which side is causing the problems.

I know with my a4 it was on the passenger side because only when I made a left hand turn did it make more noise. On right turns it was quiet.

[ldsbeaker]

Well wheels bearings usually make noise at certain speed, so I guess you could justify that if you dont reach that speed. I still think you should be able to tell the difference. From what I know diffs usually click/clunk when they are having problems.

I don't agree.
My bearings have been degrading for about 20K miles (I'll fix them eventually, dammit!) and they make more noise the faster I go. It's almost unbearable at highway speeds.
Mostly it's the drivers side one, and now it makes that "rowr rowr rowr" sound around right hand turns.