Need help figuring a sound out, just a wheel bearing or more

[siberian_divide]

Hello, I have this issue with my '07 Legacy 2.5i, 4eat. I am about 100% sure I need a front passenger side wheel bearing. There is a lot of brake dust accumulating on the rim on that side, and at times I can hear a noise coming from that side of the vehicle. The dust cap was not on the rim when I bought it, and assume that has killed the bearing.

There is this other sound that I need help discerning, the best way to describe it is between a humming and a whirring while hitting the gas. When I let up on the gas, this sound goes away. I notice this at speeds over 40 mph in general. I hadn't though much of it before, figured it was just a normal operating sound, but I did read a post about noises like this during acceleration can mean a differential going bad. I am hoping I can get some opinions whether I should be worry and what I could do to further troubleshoot this concern. I bought this Legacy used, only has 50k, and I drained all fluids and replaced with new when I first bought it, all fluid levels are fine in the diffs and trans, no leaks. I appreciate any help with this!

[d1giPhux]

A wheel bearing will sound like a squeak / rubbing metal sound.

Sounds like your brake caliper may be partially stuck / froze? Funny thing is.. my friends dad is always saying to me about how the calipers freeze up on subarus. LOL. hes old.

the whirring / humming noise? Does it sound like a ticking? Sounds like something one of my cars does.. not sure what it is either. But on that car, the tick goes away when you pull the ebrake a bit. Not sure why, I think it has something to do with drum brakes. Which i'm assuming your car doesnt have.

Does the sound occur only in a straight line?
When turning left or right and accelerating?
Can you FEEL it in the steering wheel / car seating area?

Give some more details. Could be the axles possibly as I have had to repair that on my 99 before. It was more of a clicking / grinding sound / feeling while accelerating.

[siberian_divide]

I think Subarus do pretty well with their calipers, our Impreza took 275k miles before they started sticking and eventually seized, only because the boot disintegrated. I don't think the caliper is frozen at all, the pistons compressed freely when I replaced the pads. One thing I did notice was that there was some rust corrosion on the rotor, I am considering pulling the rotors and having them machined. I have four wheel discs.

That shouldn't have anything to do with the noise I'm hearing though. It's not a ticking, I hate describing noises, but it almost sounds like a motor turning on when I hit the gas. Then it's silenced when I let off the gas. I was told by one that it could be one of the diffs starting to wear and fail, which is of course my biggest fear. Is this just normal and am I just listening too hard for sounds? It seems to occur all the time, going straight or through turns. I don't really feel any vibrations in the steering or in the cabin either. My current plan is to start with the small things, brakes and possibly a new wheel bearing to see if that fixes things, but it's just odd that it makes that noise when I accelerate. I had read something about Subaru including wheel bearings in the powertrain warranty? I'm wondering if I should take it to a Subaru dealer if that's the case. I just don't trust them or most other mechanics I don't know in general.

Not sure what else info I can give to help diagnose, if I could get a good recording of the sound, I'd post it.

[Kiwi GT]

Wheel bearings don't care if you're on or off the gas. Sounds like a diff to me.

[siberian_divide]

So, if it's definitely a diff, and I took it too a Subaru dealer, is there any chance of getting them to fix it under the powertrain warranty, or will they not do anything until my car won't move anymore?

[siberian_divide]

Kiwi, what diff do you think it most likely would be? The sound is close to me, so that would have to be the center diff. Only thing is that I've heard that center diffs will give you the torque bind, and I haven't experienced anything like that.

[d1giPhux]

Wheel bearings don't care if you're on or off the gas. Sounds like a diff to me.

yeah.. the wheel bearing will squeal as long as the car is moving if they are bad. However, when my axles went bad in the front of my car.. they would only make noise when accelerating into a turn. very weird. However that noise was more of a clunking rather than the noise you describe. Maybe try to get a sound file of the noise if possible?

The reason i asked if it was the brake caliper freezing is.. you said you see a lot of brake dust on JUST that one wheel. Clean your wheels off completely, and check to see if that wheel is generating more dust then the rest of them.