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 S320 Cracked Driveshaft Flex Discs May Cause Driveshaft Movement/Vibration
Mercedes-Benz S320 Problem
Average Mileage: 193,500 mi (187,000 mi - 200,000 mi)
Visitor, 1999 Mercedes-Benz S320, 187,000 mi
Not complaining, The '99 S320,6cyl. Short, is one of the best I have owned-apart from cost to repair- it has been a good comfortable car. Lately it begun to sound kind of rough under and close to the rear of the car. One day it I smelled something like a metal grinding smell. Took it to the dealer and they diagnosed differential metal pieces from grinding...for $2000 they installed a used from a car lot rebuilt to be used with one year warranty.
Works great so far.
Visitor, 1996 Mercedes-Benz S320, 200,000 mi
Driveshaft fell of at 60 mph. Riped the wiring, brake cable and caused the car not start afterwards