Had the tyres fitted on front, waiting for rear ones next week. I have since noticed an oily smell after 20 mile drive to work (60mph) dual carriage way. I am thinking that the rear diff is under extra strain as fronts are full tread, rear a little in the thin side. I'm hoping that once rear ones fitted, it will stop smelling as doesn't do it on short drive. I figure rear diff is getting hot. Anyone advise?? You think its worth servicing the rear diff?? New seals etc, just to freshen thinhs up?? Ideas welcome.