There's play between the spider gears, then play between the ring and pinion, all of that plus wear and tear over the years can add up to a lot when it finally makes it to the wheels.
If you turn the wheel with the other locked, in an open diff the spider gears cause a increase in the ratio, which is something like a 1:1.5. So that can exaggerate any gear play further. This is why a one wheel peel is bad, your tire is actually spinning faster than what your speedometer is reading, and will burn up thrust washers and spiders fast.
In other words it's normal, whats not normal is being able to turn the wheels more than 1/4 turn and nothing happens. This can mean badly worn spiders and/or ring and pinion. or bad clutches in a LS.
This amount of play is perfectly normal in a locker such as a Detroit, I can move my wheels almost half turn before engagement, this is part of the lockers design.
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