the 1/2 shaft joints were held stationary while checking the diffy slack? This is usually hard to do unless you have a helper. The gear lash in the diffy is relatively small and using the wheel rim to check I noted for the 1/2 shaft joints is not reliable method.
You did not say how much slack was in the 1/2 shaft joints at the wheel rim?
If I was checking the diffy slack I would disconnect the driveshaft at the diffy input and hold the diffy output flanges at both the inner 1/2 shaft joint, then slowly rock the diffy input shaft to feel the slack in the diffy gears.
