I have a customer with a fairly new 9560sts, (600hrs) that has suddenly developed a sever vibration. It seems to be comming from the propshaft to countershaft area everything else disconected. We have stripped and checked the countershaft box all seems good, i stripped and checked the drive in the engine bay seems fine. The center bearing is perfect, the only time the vibration goes away is when i disconect the propshaft, then all is fine. I have disconected the jackshaft belts etc but same sever vibration. The yoke on the countershaft is tight and the electric clutch bearing is good. Has anyone had a similar problem?Could the propshaft suddenly go out of balance with now one ever touching it and all the cross bearings are good.?