I have a 2000 pathfinder and i drove it cross country from tennessee to alaska with about 800 extra pounds of crap.I got there and took all the stuff out and now my back end is squeaking. Any ideas of what might be squeaking?

Suspension control arms, shocks, spring isolators, exhaust hanger, spare tire, I dunno. Try having someone bounce it for ya while you look underneath and try to pinpoint what's squeaking.