Help diagnose light rubbing noise in rear of car

[FleaDog]

Hey guys,

Over the last 2 months I've noticed an abnormal noise/sound.

2006 sti
44K miles

Onset: Seems to have started around a couple months ago out of the blue. Car is 'barely' driven on the weekends when I get a chance. Put 1,000 miles on the car in the last year. (Have beater car that I daily drive, and aside from that new baby). Drive 'spiritly' ('normal'); no drag racing, track, etc.

Contributing factors (rear of car)?: BC racing inverted coilovers installed in May. Already has lockdown bolts, Perrin PSRS (stabilizer bushings in the rear end around the rear diff, crossmember, etc. Stock wheels and tires. No issues with wheel bearings or brakes ever.

***Location: With the windows up, I can definetely localize it to the rear of the car. I can't tell if its right/left side though. With all the windows down its hard to tell where its coming from (front/back/left/right).

Quality: It sounds about the same as when the pads contact the rotors when the brakes are cool when the brakes are applied - a light, rotational/circular rubbing noise that increases in frequency with the speed of the car. Not squeeling/squeeking, loud/harsh, no pops/bangs... doesnt go away with the brakes or ebrake being applied/released... doesnt change with different DCCD settings, turning to the left or right, or cornering. Its the same going forward or reverse. It Doesnt change on/off throttle, and is the same coasting with engine on or off. The car seems to drive fine despite the noise. It has stayed the same since I first noticed it.

Problems ruled-out:
- Rear Brakes (pads/rotors/shields/lines) look and seem to be working fine.
- There is nothing contacting the drive shafts, universals, axles/CV's, hubs, brakes, wheels/tires (exhaust, etc).
- Rear axle nuts torqued to spec.
- Universal joints look fine on drive shafts.

What I've found so far:The rear diff has a leak once again. It already happened once after purchasing the car and a seal was replaced by the dealer/warranty. Fluid level inside was fine at that time. That was 2 years ago. Heres how it looks, the car was parked for about 2 weeks after it was last driven, and there was only a small spot on the floor, so it doesnt seem to be leaking much at all.


^^^ notice fluid on the right side of diff


^^^ spot on ground under rear diff

So, could this noise be related to the rear diff, possibly low fluid in it from a leak? I am not sure if this is a 'red-herring', or I should be looking into other potential problems or causes. Any input appreciated. I am still in warranty so my next step looks like a trip to the dealer.

[RyanG]

ould be rear diff related. Does the noise change when turning? ie weight transfer to one side

[FleaDog]

Originally Posted by AREA1320

ould be rear diff related. Does the noise change when turning? ie weight transfer to one side

Doesnt seem to change when cornering or turning in either direction. Will take her out into a bigger lot to get a better listen.

[FleaDog]

I finally had some free time today to take the car out and get a better listen.

The sound appears to be eminating from the rear brakes (pads) by way of the emergency brake.

It went away after I drove around a good bit and really hitting the brakes. It would only recur when I stopped, and applied the ebrake. After I undid it and resumed driving - it would be right back. It also went away after I soaked the rear brakes/wheels with my hose. I guess when the ebrakes are being applied, and then released the pads are somehow not being fully released and then rubbing on the rotors.

The recurrent rear diff leak appears to be unrelated, but needs to be fixed nonetheless.

So it looks like the ebrake needs to be adjusted somehow.

[FleaDog]

Update from the dead, the one of the return spings on the ebrake shoe was busted.