That could possibly be
Did we lift the front and pull on the wheel for bad ball joint and or bushing?
If not go right to the driveshaft
Yes i lifted and checked all 4 wheels for bearing or tie rod/ball joint play. They all felt fine. Ill have to try to stuff myself up under the car and feel around the driveshaft. As far as the jurid needing to be flexible, ive owned quite a few cars and trucks that had good old fashioned driveshafts and never noticed any real vibration from them, which is why I said about a solid replacement for the rubber jurid. I would think it would be fine as long as it was properly balanced.