Any advice on how to quiet the grinding and droning noise from the diff in a 2004 m3 with 145,000 klms . I live on the Gold coast in Queensland Australia and don't know where to take it to have it assessed. I have had the diff oil changed 3 weeks ago with the Castrol recommended product, but , I feel the noise is still getting louder. I have put in into neutral and coasted and listened and then back into gear and the gearbox adds to the noise only marginally. HELP.