[blykins]

Play in the rearend is normal, it's just gear backlash. It's difficult for us to give a unit of degrees as a standard, as backlash is measured in thousandths of an inch with a dial indicator on the ring gear.

However, if you were coasting to a stop, rearend play would not be the culprit here.

A chassis dyno would be a good way to check everything out, but I would look for something contacting/rubbing something else, or maybe something in the brake system.