Thanks for everyone's input. I wrongly stated that compensating chain existed originally. Even though 22 floors, there were no comp chains before. We added two whisper flex WF20 per counterweight and shallow pit guides. We tried drifting the empty car and the vibration could be felt as the speed approached 350. So it does seem like a mechanical problem. There is rubber isolation between the platform and the sling, but how effective it is I do not know. It is interesting about the comment made in regards to whisper flex rollers. I am wondering if this could be the source. We will try running without guides and see if that makes a difference. Also I like the idea of the half full water bottle. Will definitely try that out. I appreciate all the input.