A vibration felt through the center floor of the vehicle can be caused by cracked and/or shredded driveshaft flex discs, resulting in excessive driveshaft movement. If not repaired, damage to the driveshaft center support bearing, transmission, or differential can occur.Google+
Car Problem Reports
Mercedes-Benz CL600 Cracked Driveshaft Flex Discs May Cause Driveshaft Movement/Vibration
Mercedes-Benz CL600 Problem
Average Mileage: 81,666 mi (70,000 mi - 100,000 mi)
Visitor, 2002 Mercedes-Benz CL600, 75,000 mi
flex discs caused vibration in drivetrain and inside car.
Downshifting manually with transmission will show clear signs of usage and replacement will make it smooth as butter.
rear diff pinion seal and flex disc cracked