so as per any new 'used' vehicle i buy, i think its wise to swap all fluids, just wanted to verify with y'all as this is my first GM.

trucks 4x4, auto 5.3L with the auto4wd option.

so heres what i've found and wanna verify

motor oil: 5w30 is ok?
tranny: dextron VI
tcase: auto track crud from stealership
front diff 80w90 or 75x90 synthetic
rear diff 75x90 synthetic

going to do motor, diffs and tcase this weekend. tranny maybe next. (dropping the pan for the filters a pain)
was also wondering if i can run 80w90 in the diffs. rear looks like a 10bolt, and i don't think it has any traction aides.