.006-.010 A lot of the time it's not the backlash you hear. It can be spider gear wear or axle splines tend to roll as they wear out or splines in the axle gears.
THIS RIGHT HERE. It all adds up, especially going from reverse to forward. The splines on one side twist, all the spider gears "add up", the pinion moves, and then the splines on the other side finally move.