strange noises appearing to be from rear

[One Carefull Ow]

I have a R Reg C200 automatic, with around 105,000 miles on the clock.
It is regularlry serviced. Over the last 2 months I have started hearing a strange humming/whining noise when driving. It seems to be at its worse at around 70 mph. It also seems to be very apparent when slowing down to a stop. I know it is not the bearings as I had these replaced and did not make the remotest impact on the noise.
Any idea what it can be?

 

[Parrot of Doom]

Check your tyres. I had a similar issue on an Audi A4 years ago, tried everything and eventually found one of the tyres had a bulge. You wouldn't believe the strange noise it made, entirely unexpected.

 

[Howard]

Diff ?