Car in question is a 2001 Subaru Legacy sedan with 140k miles. There's a loud woomp woomp woomp noise audible inside the car, and is definitely something in the rear. Front wheel bearings were done within the year. How can I tell if its the bearings in the diff or the axles?
Worn wheel bearings usually cause play in the wheel. If the noise changes while on the brakes in neutral, that's a good sign that it's not something in the diff.
Subaru wheel bearings can be noisy without the play. It's very likely the bearings.
Yeah, most likely the bearings. Wheel bearing noise will typically change during a 'lane change' type maneuver, diff noise won't.
4 jack stands and "drive" it in place. The noise location should reveal itself then.
I don't work on a lot of Subarus, but I've seen plenty with bad wheel bearings.
Yep achey breaky wheel bearings are a known Subaru weak point.
Agreed. Also, diff noises usually change depending on the load on the diff, so if you're cruising on the highway in 5th and go from full throttle to no throttle, a diff will sound a lot different but a wheel bearing noise won't change much at all.
Something about laying under it on jack stands while driving is a little bit frightening to me. The idea had crossed my mind though.
Would draining the diff to look for metal be useful in this case?
Don't touch the diff, and you don't need to be under the car.
mikeatrpi wrote: Would draining the diff to look for metal be useful in this case?
Not really, it's possible for the bearings to cause trouble without getting metal particles in the oil.
Car off, raise both rear tires by jacking up the rear diff. Front wheels chaulked. Car in neutral and ebrake off. Spin rear wheel on one side and listen. Go to other side and spin and listen.
Dial indicator and a magnet base, specs should be in the manual. It highly doubt it would get loud without being worn out of spec.
Diffs whine/howl (loose bearing misalign gears), wheel bearing are more of a groaning/growling.
They are tapered roller bearings not the strongest and subies tend to eat up bearings/bushings like audi's
also swerve side to side and see if the pitch changes, if its a wheel bearing it will.
When you swap in a new wheel bearing (assuming that's the noise you're hearing), make sure to check the grease in the new unit and ideally, repack it with known good grease. That should extend its life a bit more.
So for various reasons, I'm finally tackling this job. The passenger side is almost fully apart, but the driver's side is being stubborn. The axle shaft is stuck in the hub. I'm debating if I should just pull the CV axle too, and load the whole mama in my press to get it apart. My google abilities are lacking; there are tons of instructions for front CV axles but very little for the rears. Haynes says I need to remove the rear diff to get the axles out. Huh, really??
In reply to mikeatrpi:
Pop ball joint and tie rod, pull out on knuckle with weak hand while hammering on it with the air chisel fitted with a dull pointed driver. That's what the dimple in the end is for!
Kenny, this is the rear... removing everything appears to be a huge job, so I'm hoping to find a way to get the CV out, still attached to the bearing assembly.
Just to verify.
Axle nut Is off
Caliper is off
sensor is off
Long bolt is out
I then use a big bearing puller to push the axle out if its not cooperating. But that usually only happens with northern transplant subies.
After that its all downhill with a hub shark.
Axle nut is off; caliper, bracket and rotor - off. ABS sensor is removed. I don't know what long bolt you're talking about, but the four 14mm holding the bearing assembly are also out. I got the passenger side apart using a puller to push the axle through - but the driver side is being rather stubborn.
Thank you all for the tips.
Crap!
I was thinking Impreza even though you stated Legacy. With the Impreza you have to remove a long bolt for the lower arms so you can pull the hub off the axle.
Anyways on the Legacy I really dont have any secrets or anything. After unbolting the 4 bolts on the hub I just give a liberal dousing with ATF/acetone (or your poison of choice) and a slidehammer with adapter.
Ive done really rusty hubs with an air chisel to separate it from the knuckle, this will likely screw up the mating surface and you'll need to draw file it back flat though.
Run it in the air, put a stethoscope to the different possible culprits, done.
Day 2 update: I ended up removing the entire rear suspension arm (which was surprisingly straightforward and easy to do), and popped the CV out of the diff. I have the whole thing precariously positioned in my 12 ton Harbor Freight press, sitting in my driveway, loaded. I tried using a FWD hub puller from autozone to push the axle out, tried the air hammer, tried my ball-pein hammer with a drift - then all of the above with and without liberal coats of PB Blaster and / or heat from my propane torch. I peen'ed over the head of the CV shaft so bad that I couldn't get the nut back on. While I hate destroying stuff, this battle might be lost. Is it dumb to drill out the cv shaft with the hope it will relieve pressure inside the hub? Another thought is to take it to a shop with a larger press. Eventually it will let go - I think!
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