How to tell if center diff is ok?

[97gsxturbo97]

I have the center diff out of the car. The transfer case was bad and I am inspecting all the parts before I put it back together. How do I tell if its ok. I can hear some noise when I shake it and I can hear some noise when I spin it by hand. What should the thing be doing? This center diff is out of an auto trans. Also should the shaft that goes through the transmission case all the way to the transfer case have play in it if the transfer case is out of the car because I can move it up and down a little.