What kind of gear oil for 8 3/4? Why not synthetic gear oil?

I run Mobil 1 synthetic gear lube in all my rear ends (and front ends on 4x4). Mobil 1 does not require addtional friction modifier and I do not add it in the limited slip diffs and have not had any chatter problems.

When I rebuilt the rear end in my Barracuda I do recall that the Yukon gear instructions recomended a 500 mile break in with conventional gear oil before swapping to synthetic gear oil which I did. The rear has been trouble free and quiet for over 30k miles so far.