99 ford mustang rear end noise?

[Cory L]

while i was doing the brakes (pads, rotors and calipers all the way around) i did a quick shake down, front end was fine all nice and tight no problem (think there was a bearing on one side, no problem) now on the rear end this is where i'm not nearly as experienced as i would like to be one side was loose while pulling on it (in and out parallel to the axle) and while rotating the wheels there was a little play before it caught (drive shaft started moving) normal? ok that was the passenger side, now on to the driver side, there was a click both ways before it caught, also the seal is bad (know that) and there is the same small movement parallel to the axle (push and pull) i'm thinking either a bad bearing or the drive shaft is loose generally (based on small bit of knowledge that i do know) either the differential is bad or a C clip is loose? or is this normal? it is NOT the drive shaft! i checked it and everything else is nice and tight checked the u joints as well (all OK) just that small click click click (both ways no matter what way i turn it) worries me any opinions? guesses? its a 99 mustang with the 3.8L 6 cyl straight coupe no gt or cobra sadly. ALSO (i know i'm asking a lot here) if the bearings are bad is it that nasty interference fit with the steel ring? where you have to get a VERY sharp chisel to break it? yes? no? if no what type is it?