Have you removed the end play adjuster from the posi unit ?
If not I would and go from there wrench
You do not want the axles to have any preload on them with both axles installed in the housing with either type of the "green ball bearing type" axle bearings tsk
So yes you should have a small amount of end play, say from .003 to .015 scope

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)