Subaru Repair: Subaru Tranfer Case?, wheel drive car, wrx impreza

Question
My 2002 wrx impreza  has been making a whinnying sound while on the move.more audible while coasting and sound decreases as vehicle slows to stop. at random intervals there is an air release swoosh noise that made me think that it may be turbo related..At first my mechanic told me its the wheel bearings...now he says that the noise is originating from the transfer case and the whole transmission must be replaced.I read other posted answers about how tire size can affect the AWD system.bout six weeks ago i replaced a single blown tire. Tire shop tried to match size as much as possible.however i do not know if there is more than a 1/4 inch difference..there is no clunking or thumping sounds. my questions are these Do you think that it is indeed a transfer case issue.? If so will the dealer be able to easily identify it? If i replace all tires will the noise       cease? Or is the damage done? Please advise...

Answer
Subaru doesn't use a transfer case.

If it is  a manual transmission it uses a Viscus coupler, If it is a Auto transmission it uses a Computer to engage a Solenoid to activate the Transfer clutches.

Usually the symptoms are Torque binding (slow speeds turning tight) the car feels like it is binding.  Like a Four wheel drive car that is stuck in four wheel drive.

The noise could be related but it could be something else as well.  Lots to go wrong in a Transmission.  How are the fluid levels? and have the fluids been serviced regularly.

You should never run different tires they all need to have the same amount of tread and like tread design.