I have double checked th u joints, there isn't any play in them, very solid. I'm going to change th tranny mount tonight and make sure the driveline hasn't lost a weight. I'll let ya know if that helps or not.
Checking the joints for slop is only one of the checks, they also need to be checked for being seized and the only way to do that properly is remove the shaft at the pinion yoke, pull the entire shaft assembly out of the tranny and physically check that all the cups are free not frozen or feel lumpy. This condition will also give you a vibration.