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Diff diagnosis

91 legacy AWD w/240,000 miles. I'd like to get another 20-30 out of it if I can.

I'm getting a howling from the back of the car. Loudness is roadspeed dependent not engine speed dependent. It seems to have been getting louder in recent weeks...so SOMEthing needs to be done pretty soon.

1) How can i diagnose whether it is the rear diff or possibly a wheel bearing (one side or the other). I've tried jacking up the car, but that then unloads the bearing and I can detect no noise by manually turning the wheels.

2) Assuming it to be diff, are these things solid enough that a junkyard unit would likely be usable (assuming I can check vehicle mileage and it's in the 100-150 thou range). What year units would interchange with

91 Legacy?

TIA (Thanks In Advance)

Reply to
Mac Townsend
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You have an open rear diff, right?

Have you tried jacking up all 4 wheels, starting the car, placing in gear so wheels spin? Try to hold the left wheel so only right spins. Then do the same so left spins. If it's a problem with the diff or axle joints I'd expect you to be able to hear it when you're doing this. I'd expect axle noise to get worse, since the angle of deflection is greater with the wheels in the air. But bearing noise is likely to be quieter.

Also, while the car is jacked up you might want to put it in neutral, not running, and turn

*both* back wheels by hand (might need an assistant).

I think so. Yours lasted 240k (or more if still OK). If it it's an open diff, and it operates OK in the junkyard (doesn't make clunking noises when you turn the various shafts), I'd have high hopes for it. I'd try to avoid driveline parts from a WRX or similar car that might have seen a lot of hard launches.

David

Reply to
David

This is a piece of cake, put the car on a lift and use an automotive stethoscope. Make one...just a plastic tube will work. Most muffler shops will let you hoist it up for a minute. TG

Reply to
TG

I'm assuming you've checked your diff oil level. Could be that simple. Agree with both previous posts too. Cheers

Reply to
hippo

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