I have always been able to rock the driveshaft with the jeep in park. It moves a little bit before it engages the front gears. What else am I looking for to see if it's bad?

 

Were the joint cap sits in the yoke if it has clips or snap rings make sure they are all there I have seen them come out then the shaft will move but look fine & no I'm not knocking the mechanic you would be surprised how often they are forgotten about. The other thing is if it has straps check the bolt that hold the strap to the u-joint cap to the yoke. This might be a dumb question but dose the u-joint have a greases fitting? The other thing is grab the driveshaft were it hooks up on the rear and move it in the direction of all for caps at that point you should have no play.

 

Just ran out to my 08 the shaft has no play at all, do you have a stock shaft?

 

This can be normal because your suspension and drivetrian is going from no load or a forward load if the nose is pointing down an incline to a reverse load.

my wifes WJ does the exact same thing. it gets more noticable as time goes on because they is more ware and slack in the drivetrian.

 

keep in mind if your rotating the rear while the vehicle is on any form of a slight incline you may have the drivetrian "loaded" and will not be able to move the shaft by hand.

 

What I was talking about was holding above the slip and below to see if there was any play I have helped my brother-Inlaw for quite a while and he makes driveshaft in his business.

 

Well it gets better. I got under there to check the driveshaft with the engine running and now I hear a knocking sound. I though it was the engine but Im not sure, upon further inspection it sounds like where the engine meets the tranny, could the torque converter be knocking like that and would that be the cause for the thud as well?

 

Mines been making some funny noises lately. Been getting more noticable. When I spin it, it makes this noise. Was surprised how easy the transfer case was moving when I shook driveshaft. Sorry about crappy video. Went to edit it, but can only save as a stupid adobe file.

http://www.youtube.com/watch?v=TXHUMvhNqgc

 

Anyone have any ideas if the torque converter could be making a knocking sound?

 

Yes, the torque converter bolts could be loose. It doesn't happen often, but could be.