I use 0w 40 mobil 1. and I have no snags at all. By book and performance ford mag recommend 5w 50. But this oil is for high performance cars etc etc.

I had my diffs, gearbox and transfer box oil changed a couple of years ago and the garage used the same sort of stuff any other every day car would use on the gearbox, diff and transfer box, and again all has been fine.
I think the garage used Automatic gearbox fluid in the transfer box of the top of my head.

cheeRS