Thanks very much for the response. I got under and sure enough the rear, top two bushings are indeed loose. I pull and pry around and can't move the differential much, but if torque is applied from the driveshaft, it may very well move it much further.
I also felt the ring and pinion slack and it just doesn't seem to be excessive.
Did you have to drop the whole differential down to replace the differential mount bushings?
Thanks for the responses everyone,