I ran a group 4 80w140 in the 9.25 in my traded off 2011 ram 1500. Towed extremely heavy with it. The year before I sold it, I did another oil change to have a look at the gears. Little to no material on the magnetic fill plug and the gears looked pristine. I did not have my IR temp gun at the time but I would get it hot enough you could not touch the diff.
The manual called for 75w140 but locally for the big names, wanted 23 to 30 bucks a quart. I got the 80w140 in a 20 litre pail for 9 bucks a litre.