Wait until you have about 1000 miles on your new gears before you make the switch. The rough faces on the gear teeth need to wear smooth before you drive it hard and the synthetic will slow down the break-in time.

I'm running Mobil 1 in engine(10W30), tranny and transfer case(ATF) and diffs(75W90)

93 4X4 ext-cab, auto, SR5, 3.4 V6, supercharged, 2.1" pulley, URD fuel mods, Aquamist WI, IPT valve body mod, dual cases, 4" superlift, Alcan springs, 33 BFG MT, ARB locked front & rear, 5.29 US Gears, RB 1" BL, 1.5" BJ spacers, TJM T-17, Warn m8000.