Not in unison? How’s that work?
So my tcase may need a new bearing too? Guess I’m going to order one of them up when I get a chance. If I remove the shaft and it gets rid of the vibration, I may drive it 2WD cross country this summer depending on how soon I can fix it.
The support bearing doesn’t seem like a great design.
It looks like the driveshaft moves slightly, but the yoke doesn't. That's a sign of play in the ujoint.
There are polyurethane support bearings available. Some are even greasable. They cost 3-4x as much though.
When you take the rear shaft out, replace all 3 ujoints and the support bearing. Most efficient for labour.