not intending to commandeer the thread, but ive had a similar problem occur to me today on my way home from work, but its a squealing noise almost like a break pad rubbing on the rotor, and its on and off as if its a particular section being affected, its only during cruising speeds and deceleration, so not when accelerating and you can hear at low as 10km/h around the street. my car is a r32 gtst, and ive had diff clunking when its being engaged, ever since i put in some alloy rear cradle bushes. am i up for a new diff?
hope you get your car sorted out too Skizza