Rear end problem help

take it out and check backlash, sounds like you got too much somewhere, probably the side adjusters..move the gear closer if you got crazy ring gear lash. may have to remark the gear pattern. Rob says your pinion...it may not be deep enough. supposed to give it 500 miles and then change the fluids per Dr. Diff. Id take it out ASAP and find the issue. If the pattern is centered and the lash is in spec, it may indeed be break in noises. Never broke in a new set of gears but if the factory didnt either, there would be a lot of complaining new car customers!