Hi, I have a 320d 2007 Tourer, been getting a droning sound for a couple of weeks that appears to be coming from rear centre of the car. The noise kicks in at 40+ mph. Had it checked at a garage today and been told it is the diff that is making the noise and it sounds an expensive fix, certainly for a new one. Spoke to a diff reconditioning specialist and they mentioned not all BMW diff parts are easy to come by to use in reconditioning. Hopefully that's not the case though. Anyone aware of a BMW recon specialist in East Midlands? Thanks, Mark.