Hopefully this is a normal thing to happen...
2008 Rubicon, auto, in park, no hill, level concrete ground.
Talking with a friend by my Jeep - I put my foot at top of the rear tire and pushed on the tire with my foot a few times and noticed there was some play in the axle. I was surprised and braced myself and pushed several times really hard and noticed that I was getting "play" out of the axle - it looked almost like the wheels were loose (they are not). It did not move but maybe a mm, but enough to get a small "clunk" out of the area when pushed.
It does this on both sides of the rear axle - it does not do this on the front wheels. I don't have any issues with the Jeep and there are no known issues, just really surprised about the amount of play.
Try it and see if this happens on your Jeep - hopefully this is "normal" play.