Vibration or light thump or runble sound on 2001 Mercedes-Benz CL500

This is a tough question because it is a sound or vibration. It sounds like a light thump or low vibration that I only hear at low speeds, below 40 mph. I thought it was coming from rear suspension, now I am wondering if it's the driveshaft flex busing. The car has 62K, any ideas will be appreciated.

Asked by for the 2001 Mercedes-Benz CL500
There is a good chance the issue is with the driveshaft, here is some info from the common problems page:
"A vibration felt through the center floor of the vehicle can be caused by driveshaft flex discs, which crack and shred, causing excessive driveshaft movement. Not repairing these can cause damage to the driveshaft center support bearing, or, in the worst case scenario, damage to the transmission or differential"
I think he is really sure its in the suspension and not just a vibration like an old u joint type of thing
1 more answer
I have a 2003 CL500 with 60,000. My car had the exact 'symtoms' and sound. MB in Santa Barbara said the car needs a ABC pump, which controls the hydraulic fluid
in the car. There is an anti-vibrational part in the pump that keeps those vibrations from being heard. The cost for a new pump is $3,000 plus, but that's a lot less money than buying a new car!