Drive train vibration. Scratching my head.

Couldn't find a picture online. Will check shop manual when I get home.

Grainger shows something similar. Can shaped piece of rubber with a bolt sticking out of it. Was about 5 pounds if I recall correctly.

I'm sure balancing the driveshaft would cure the vibration but I have a A500/A518 plan for the near future. Will need a new driveshaft.