Originally Posted by RamTech
It's most likely a pinion bearing and, in order to verify, you need to remove the pinion gear. I recommend replacing all the bearings while you're in there.
Ill just go into Advanced Auto and order the kit sometime. I think they have Motive, Pro King and a few others and brand better than the other? and I know I need a tool to go in the axle houseing and has a nut like end on it to tighten or losen something can I buy or rent one or should I just make mine ?