Did a vibration investigation a few years back on an R-44, T/R drive shaft. Found bad shaft misalignment, to the point that the bearing next to the drive belt assembly had let go, if memory serves me correctly it was an oil filled bearing / viscous damper, the assembly was damaged to the point that all the oil had escaped. Anyway, to cut a long story short, the bearing assy was replaced, with the clutch assy re-adjusted. I only did the vibe work, didn't do the rectification, but again from memory, I belive the guys had to make an adjustment to the clutch extension distance.
Hope this helps. If you need more I can dig through my archive and see what else I can find on the subject, I think I have photos of the damage.
The aircraft had hydraulic controls, and I had only just done an RTB on it, so the Main and Tail rotors, and the engine fan were all smooth, we picked up the TRDS vibe during a vibration survey, previously the M/R & T/R vibration had kept it masked from the pilot.