I noticed today when coming to a stop going down hills today that I get a slight sensation through the wheels, best way I can describe it is like driving on crisp snow when it just compacts a little under the tyres. This is on dry flat tarmac.
I changed the diff oil with Castrol B373 Diff oil around 6 months ago. The car drives grand with no other signs to speak of, no excess fuel useage etc.
Any advice? change fluid again etc?

 

could try dropping the oil out and checking for debris