E30 whining noise (back end)

Since a couple of days I notice a whining noise in my BMW E30 (built
in the year 1988), it is a European 324turbodiesel touring which has
run about 180k. The noise is noticable from a speed of 40 km/hour
(about 25 miles I think), gets louder at higher speeds and is
independant of engine revs. It does not get louder in turns, neither
does it get louder when breaking or accellerating. The noise seems to
come from the back of the car, but I am not sure if it is louder on
one side.
The front right wheel bearing has just been replaced, I have new back
tyres, which have been balanced a few weeks ago.

Is this all pointing to worn back wheel bearings? Or should I suspect
the differential (worn of oil shortage?)?

I know there are a several posts on this board about this sort of
thing, but the descriptions seem different, in most messages I see
that the noise changed when turning.

Any ideas will be appreciated.

"Pedro" > wrote in message
om...
> Since a couple of days I notice a whining noise in my BMW E30 (built
> in the year 1988), it is a European 324turbodiesel touring which has
> run about 180k. The noise is noticable from a speed of 40 km/hour
> (about 25 miles I think), gets louder at higher speeds and is
> independant of engine revs. It does not get louder in turns, neither
> does it get louder when breaking or accellerating. The noise seems to
> come from the back of the car, but I am not sure if it is louder on
> one side.
> The front right wheel bearing has just been replaced, I have new back
> tyres, which have been balanced a few weeks ago.
>
> Is this all pointing to worn back wheel bearings? Or should I suspect
> the differential (worn of oil shortage?)?
>
> I know there are a several posts on this board about this sort of
> thing, but the descriptions seem different, in most messages I see
> that the noise changed when turning.
>
> Any ideas will be appreciated.

Probably a wheel bearing or your diff. I'd guess the diff since it doesn't
vary with turnig but a bearing noise doesn't always do that either. On the
other hand diff noises often get louder under power or engine breaking than
steady state or neutral.

-Russ.

My diesel volvo recently started doing that. As i accelerate the noise
changes pitch and becomes more penetrating (i.e. it just feels like its
going through you). I noticed to turn my head to the left it gets louder,
but to the right quieter. I dont always beleive that a wheel bearing will
show a difference in noise if it is only present at highway speed, where the
shift in the weight and direction of the vehicle is minimal. shake your
wheels down to check for worn bearings, jack them off the ground for a spin,
(slow, very).. listen for noise and feel for slack. change your diff oil..
cant hurt, maybe it will make your problem go away.

Erik

Thanks for your advice and thoughts, everyone!

In the meantime, the strange sound has decreased slowly (and by the
time I got to the BMW auto shop it had disappeared completely).

Now I think it may have something to do with saggy springs and/or
shocks, because I also hit speed bumps all too easily and the back end
is a bit lower than a few weeks ago...