Hi, I live in hamilton but my father lives in christchurch, we both have subarus I have a single turbo GTB and he has a REV D b4 , I have recently been to visit him and he showed me that when hes turning into car parks and doing U-turns ect, there is a real bad shudder and a banging noise and a whining noise in cabin that changes depending on the cars speed ,this only happens when the cars been driving for about 20 mins and is fully warm . I suspect the centre diff is sutffed, He needs to take it to a mechanic that is good with Subarus in the Christchurch area and that has a courtesy car or something. Any recommendations?