.001 is pretty thin. I got measurements around the pinion head that varied more than that (on the same head).
BTW, I would replace the axel bearings while you are in there. They are pretty cheap, and easy to do. Plus you save the mess of breaking back into the rear end to replace down the road.
You could rebuild the trac loc for the same reason (I did). But that might be overkill if your's is running well.