I want to switch to AMSOIL Severe Gear in both the front and rear diffs. I don't tow or haul with my truck frequently, but I might be installing a camper shell and heavy toolbox, and I might tow (rarely) in the future. It seems like the ideal solution would be 75w-90 in the front diff and 75w-90 in the rear diff, but I'm wondering if I could get away with 75w-90 all the way around for the sake of only buying one type of gear oil. What viscosity do y'all run? Thanks!