Subaru Impreza 2005: GL front differential shudder

I am getting a shudder in the steering of my 2005 Subaru Impreza GL when turning slowly such as coming out of a parking spot at a shopping centre. I took it to a mechanic to have it serviced and was told that the front diff is on its way out and that it was a common fault with Subarus. I contacted a Subaru dealer and explained the problem to the service department and they said it could be a solenoid at the rear of the transmission or the clutch could be grabbing and would cost between $750-$950 to fix. These quoted prices seem to me to be quite extravagant. Have you heard of Subarus having front diff and transmission problems when the vehicle has only done 122,000 km. I would appreciate you opinion of the above.