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Spec.B rear diff issue possibly?


dbrunone

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A few days ago I noticed a soft humming noise while on the highway, most notably at about 60mph, but audible above 35mph. Noise follows wheel speed, not engine speed. You can only hear it if you have the radio off, but it is noticeable. Sounds exactly like a small Cessna airplane is about 2000ft above me, sounds like it's coming from the back of the car.

 

Looked around underneath, found a front CV boot that had come loose and splattered grease everywhere. Hoping that was the problem (and because it needed fixing anyway) I had that axle replaced. Noise stayed exactly the same.

 

I immediately suspected wheel bearings so I jacked up the car and tried to shake the rear wheels, no movement. I also spun them, felt no grinding or anything. I grabbed each axle and shook it with my hand...joints on the wheels were solid, but the joint connecting to the rear diff (on both sides) wiggled very slightly. For comparison, I shook the front axle connecting to the tranny and it is solid as well.

 

I also noticed a good amount of oil on the outside of the diff. This appeared about 6 months ago but I chalked it up to a leaky fill bolt. Diff oil level was never less than full, so it was never run dry. Could this be where my noise is coming from? I can do a lot of work on cars, but tearing apart a differential scares me. Also, I believe this car has the R180 diff, correct? Being non-standard makes me think it will be expensive too.

 

So should I drive it til the noise becomes unbearable, or have it checked out immediately? If immediate, should I go to a Subaru dealer or a transmission shop?

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When I drove on a donut in the rear for a short bit, I would always hear the rear diff. It was a mid-high pitched whirring noise, not sure I'd compare it to an airplane. Of course, if yours in failing, it could be making a totally different noise...

 

But I've had a rear wheeling bearing fail that sounded similar to what you describe. I too checked it in my driveway like you, but it seemed fine. Ultimately I had the bearing replaced and the noise was gone.

 

I personally like dealing with my local Subaru dealership. They're honest about what needs attention and what doesn't, and they're mod friendly. I've had much better experiences with my dealer than the local import shop. Other dealerships though may well be different.

MODS: PW TMIC, Cobb catted DP, HKS cat-back, AVO filter, Bren e-tune; Konis/Epics, Advan RCII
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Most likely its a hub/bearing.

 

Seat in the back seat while someone drives the car, you can hear a lot from back there.

 

When your on the highway taking a flyover listen for the hum to change pitch as the cars weight and angle changes.

 

 

Yes Spec B's have a R180.

305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD).  CHECK your oil, these cars use it.

 

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Most likely its a hub/bearing.

 

Seat in the back seat while someone drives the car, you can hear a lot from back there.

 

When your on the highway taking a flyover listen for the hum to change pitch as the cars weight and angle changes.

 

 

Yes Spec B's have a R180.

 

The reason I think it's the diff is 1) the diff has oil all over it, 2) the axles going into the diff are not super-solid. Perhaps it is both....?

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Does the sound go away when cornering ? This how to diagnose wheel bearings

 

If it was the diff the sound would go away when you let off the throttle

Now that's thinking out of the boxer!:lol:

fyi all 05 + legacy's have built in code reader

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Its hard to tell because I can only hear it above 40mph, and most noticeable at 60mph....I drive aggressively at times but taking corners that fast is tough! Letting off the gas doesnt change it though...
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No but super light cornering you can do it on a strait road at 50 mph

Just slightly curve left and right. The bearings work on a cantilever and just the slightest cornering unloads them and makes the noise go away left bearing noise would go away when turning right and vice versa

 

If it doesn't change from on and off throttle it's not likely the rear diff or any diff.

Now that's thinking out of the boxer!:lol:

fyi all 05 + legacy's have built in code reader

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I'm thinking wheel bearings.

 

2007, the car is 7 y/o, nothing last forever.

 

The other day someone posted a link to all 4 hubs for like $150 somewhere. I think Jmp added to this sticky in the 4th gen forum.

 

I used Moogs on my wagons rear and they work great.

305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD).  CHECK your oil, these cars use it.

 

Engine Build - Click Here

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  • 1 month later...
I'm having a similar issue in my 05. Noise is noticable going straight at around 40+. Gets louder up to 65-70, then stays about the same. when I turn left it gets louder. turn right it quiets down. Changes slightly between being on and off throttle but not much, Really hard to tell with the exhaust noise it might not at all. Going to change rear diff fluid and the wheel bearing.
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  • 1 month later...
Its hard to tell because I can only hear it above 40mph, and most noticeable at 60mph....I drive aggressively at times but taking corners that fast is tough! Letting off the gas doesnt change it though...

 

I have had the same issue and was curious if was the wheel bearing. Before I purchased my spec.B I read a lot of reviews that said that these cars went through wheels bearings. I figure thats my issue too. Although, its not that noticeable everyday; only sometimes do I hear it.

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