I'm fighting a driveshaft vibration problem and looking at the center bearing and double C as the culprits.

Can someone tell me how to check the center bearing? I can grab the driveshaft and move it from side to side a bit. It does not have any loose slop. The rubber cushion just gives and allows it to move. Is this normal? How much movement is allowed?

Any advice on how to check the double cardan joint would be appreciated as well. I plan on disconnecting the shaft and looking at the joint closely on a bench. I don't see any slop in the joint at all but it could be binding.

Thanks,

Shedman