Diagnose my problem
 

Alright, so the the problem iv'e been having recently is under normal acceleration between 25-55mph the car kind of hesitates. I took it into the shop today and had them put it on the lift.. there is absolute NO PLAY in the rear driver wheel and very very small amount in the rear passenger. (The wheel wont move AT ALL when lifted) (no ebrake on/in Neutral)
My guess is the diff is going to shit out again on me here soon (just replaced 2 yrs ago...) but want to be sure.Diff fluid was replaced within the last 6 months. It is my DD so I need to figure out this problem fast before more damage is done. Any help is appreciated. Mods listed below related to the area.

1998 Firebird Formula
6-speed (T56)
KYB AGX Shocks
KYB G-A-J Shocks
BMR Lowering Springs
BMR Adjustable PHB

Are you saying one wheel won't turn in neutral or both won't turn?

Sounds more like a brake problem than an axle problem.

Al 95 Z28

Second checking your brakes first