Robynsmerc

Hi all, I have just joined up here so all new to me.. I have a 2012 cdi250 coupe which I bought 2nd hand with 4000 Kim's on the clock.. It is a great car and have had very few issues with it so far.. Just a query not on a noise that seems to be getting louder in the rear end.. A whine while driving and my husband seems to think it sounds like a pinion bearing or differential noise. Has anyone had this problem with this model? It has about 80000 Kim's on the clock now but don't expect those problems with such a good car.. Any ideas would be appreciated