I have got a 2001 WRX auto/tiptronic transimission. I hear a whinning noise from the rear wheel more like another vehicle overtaking me mainly in speeds of over 80Kmph.
Then theres a cranking sound mainly when shifting on low gear.
Could this be a problem on the rear differential
Yes. Check the propeller shaft U-joints and at differential flange where it is joined by the propeller shaft, shake it up and donw and check for excessive free play. There should only be minimal movement.