when do I change and what type of oil to use for the differential? on 2009 Chevrolet Avalanche

what is the cause of a clicking noise in my right rear wheel? click goes quiet when I lift the wheel off the ground or make right corner turns. clicks started about a month ago.

2 answers
ck with local parts house for info
Bearing starting to go.on my 07 the rear bearings got pitted at 20,000 miles and luckily it got done under waranty