Well, there just simply isnt any way to change the setup. Shimming this would only make it tighter. I just put a new diff case in the truck today. I certainly hope this one lasts longer. Time to take it out and fire it up.
ORIGINAL: i8tweety
My over-tightened screw theory came from the diff case cracking straight through the screw hole.
With any luck, the problem is gear mesh, and can be corrected by taking your time and adjusting the back-lash when you drop it in the new case.