Rear Differential

[Scott]

I have a '94 Legacy which is suffering from a humming noise from what sounds
like the rear tires. I was told by a mechanic today it was the rear
differential, but a friend of mine is not convinced. He thinks it's a
bearing.

Does anyone know what a rear dif sounds like when it's starting to crap out?
The noise gets louder the faster the car goes.

Cheers!
Scott
*take out the oogabooga to reply directly*

 

[S]

Hi Scott!

I have a '94 Legacy which is suffering from a humming noise from what sounds
like the rear tires. I was told by a mechanic today it was the rear
differential, but a friend of mine is not convinced. He thinks it's a
bearing.

Did you rotate and/or replace the tires to eliminate that as a
possible source? 'Bout the only other suggestion I can make is to run
the car while up on jack stands and listen carefully. Use a mechanics
stethoscope. Do be careful if you do this, lest you become a candidate
for the Darwin Awards ;-)
You might also remove both rear half shafts and see how that affects
the noise, but that wouldn't be conclusive in an AWD car, as the rear
diff is _still_ spinning.
I'd bet on tires first, and rear wheel bearing second, if for no other
reason than it's cheaper to do wheel bearings than to service or
replace the diff.

ByeBye! S.

Steve Jernigan KG0MB
Laboratory Manager
Microelectronics Research
University of Colorado
(719) 262-3101

 

[nItpIk]

Experience would lead me to believe it is a wheel bearing .. had to replace
many wheel bearings, never had to do anything with the diffy. Any fluid
leaking from the diff? Have someone drive while you sit in the very back of
the car, listen to the noise while sitting in the center and see if the
noise comes from the center or is mostly right or left. Take a long
screwdriver and put the tip on a part of the metal car body close to where
the struts/shocks fasten to the body and put your ear on the handle, see
which side is louder. If it is decidedly on the left or right side, then
definitely a wheel bearing assuming it's not some half-shaft noise, which
has a different kind of sound. It's not likely that you have a wheel
bearing on both sides go out at the same time.

 

[Subaru Group]

Sounds like the infamous wheel bearings! A subaru parts guy told me to make
sure the new bearings are well packed with grease as they tend to come a tad
on the DRY side!

- Dan