I have any trusty 2001 4wd sportage back again ( new engine (used)) I'm attemping to do some preventive maintenance. should I drop the hypoid oil in the front and rear universals, when I'm under there next time. the car has 80k on it. it was done once at 30k by the dealer. if it was done or not really done, I can't tell. I think I should, what do you guys think.

DIfferential lube is almost life time. THere are no carbon or other combustion products deposits, and unless the car is severely abused I see no reason for that expense. Never done that "on purpose".