I agree with chief on Trans causing vib but if the part of the yoke that slides into the tail shaft is worn, grooved or otherwise torn up, you can bet the bushing inside needs replacing as well. You hear a lot of talk about driveline angles but if everything is bolted in correctly it shouldn't be an issue. There's lots of things that can cause a vib including bent axles, bad bearings, bent rims, bad tires, broken mounts. You can go two ways with it, start at one end and fix or replace till you get to the other end or start with the least expensive to the most. Sucks replacing stuff that's perfectly good but at least you end up with new parts on the car and good spares for in case.