2006 Legacy GT
80 000 km
I have recently did a long drive with my car (1000 km in a day) and at the last 100 or so kms I have noticed a noise coming from under my car that wasn't there before.
The noise is like a humming/ gear groaning and is speed sensitive (definitely not rev sensitive). I can't pinpoint exactly where it is coming from from inside my car but it doesn't seem to be coming from the transmission as it would have made a noise through the shifter if it was the case.
There is no felt vibration. No vibration in the steering wheel either. The noise becomes very apparent as I drive at 60 km/h and up.
I have lifted the car and the CV joint boots are intact. There is also no apparent play in the wheel bearings.
I have drained the rear diff's oil and what came out was a very dark, almost black sludge. Is it normal for an LSD's oil to be this colour after 80 000 km or is it a clear sing that my rear diff is going?
Any advice is welcome. I still have a warranty but I am 200 km from the closest dealership and I have an extremely tight schedule at work right now so I cannot afford to go back and forth to and from the dealership multiple times. I will also need to drive another 1000 km soon and I really want to fix this problem before that.
Thanks in advance for any input.