Grab one of the rear driveshafts and try to slide it back & forth toward the wheel and the transmission, in/out of CV joints on each end. How much does it move (or how much should it move?). It is supposed to move some by design. I am trying to determine if mine has too much play in the direction parallel to shaft. Thanks.

 

Yes there will be some movement in the direction mentioned,the shaft has to be able to swing in an arc vertically.There should be less movement towards the front & rear of the car(horizontically)

 

It's hard to tell if they are worn, as there is some movement. I had some drive line play a few years ago and had them checked. I was told they were fine. I said replace them anyway and the new ones really tightened things up. Problem solved.