Driveline vibration out of now where! Help!

Could it be wrong / damaged slip yoke? What happens if the sprag is damaged? So far as U joint timing you can SEE them. Put the shaft on a bench, immobile with rags, blocks, vise. Level one end rotationally. Other ends should also be level. I'm talking about the U joint yoke ends.

Other than that take it somewhere and re-check driveshaft straightness/ balance