My 99' automatic 2.5 85k miles projects a distinct rotational whining noise at 45 to 60 mph from the left rear. Sounds just like a worn wheel bearing or bad tire.The noise sometimes quiets and even disappears while accelerateing within the 45 to 60 mph. When I let off the pedal the sound comes back. Cornering and swerving makes no difference. Up on the lift the wheel spins freely and the bearing does not wiggle side to side with no noise. So probably not the wheel bearing and I have rotated the tires twice but the sound still comes from the same place, left rear. I'm thinking about changing the rear differential (worn diff. bearing?). If anyone has any insight i would sure appreciate it. I would hate to drop $300 and a whole day and be wrong.

What Click & Clack's lackys have done to screw up the old CQ site is sacrilege. Posts don't appear until someone passes judgement on them. I'm surprised they allowed mine, since it sent you here. It took until the next day after I put it into their system. No wonder you asked a second time. And they call it a BBS. Just BS is about right.

 

I'm sorry no one over here has answered your question yet. Don't worry, they will. Usually it only takes a couple of hours. My '97 Impreza Outback doesn't have this issue, so I'm no help. Changing the rear differential would be verrrry costly, especially just on a hunch. I'm still betting on tires. Perhaps the one you rotated to that position has the same problem. Remember that spinning the wheels by hand MAY not show the problem as a tire spinning at highway speeds will have a tendency to distort more due to centrifugal force. I had an SVX that the tires looked great on, until I jacked it up all around and spun all four wheels about 60 MPH. Probably not a safe practice, but it worked. Also remember that all four AWD Subaru tires should always have about the same amount of wear to avoid driveline problems. This may mean replacing all four at one time.

Have you checked or had the rear diff checked to see if it's low on fluid? If it's low that could be your noise. Unfortunately that would also have toasted the diff. You might try moving the rear tires to the front. If the noise moves it's the tires not a bearing or the diff. I wish you luck & hope that noise moves to the front.

Since he's savvy enough to change out the differential himself, I'm sure he's checked the fluid level too. Can't just the suspected bearig be replaced?

 

I bragged about this site on the lousy Car Talk site to get him to post here, so I sure hope someone can help him.

If rotating tires doesn't change the location of the noise, I would suspect the bearing.

 

It's not unknown for the wheel bearings to go on these cars. I had one go on my 97 Outback. They said that the seal was bad which allowed water into the bearing. I ended up with pitting on the shaft at the seal, therefore they changed out the half shaft too.

 

It took a long time to get noisy on my car and it didn't show play at all in the early stages.

 

Commuter

My 97 OB developed the same thing at about 80 000 km, and in the same location, the left rear. A new wheel bearing solved the problem. If you can't narrow it down to tires, I'd put my money on the wheel bearing. Quick to change if you have access to a 10 ton press, and not a great deal of dough. Good Luck!

It has been my experience that a wheel bearing usually makes more of a rumble. Does the sound change when you go around corners? If so then I suspect a bearing. A whining sound is usually associated with a bad diff.

If you have access to a lift , you can diagnose a wheel bearing . Drive the car until it gets noisy . Put it on the rack with someone in it . Raise it up , have them drive it to speed that is most noisy & with someone under the car , listen to each wheel bearing (4) with a mechanics stethoscope . It may take the driver some finnesse to keep the wheels at needed speed , but you should be able to listen to all . Put the tip of the scope right beside the spinning CV , but don't touch the moving parts . Normal sound should be very quiet & smooth . Be careful . This is only a suggestion .

It was a bent crossmember bracket causing the rotation of the driveshaft to make noise. Who would have thought?