In answer to the "twice asked---never answered" question in this thread about whether a "clunking" sound when changing gears or relative shaft directional torque could be associated with damaged/aged flex disk(s)---YES---it can be a sign of a disintegrating flex disk. I had a 300SD which made ugly clunking sounds when switching relative torque rotation (forward to reverse, or vice-versa, or switching from accelerating or coasting into downshifting mode). I looked under the ends of the driveshaft and saw "Einstein's hairdresser" had done major work on one of my flex disks (similar to the worst photos of above posts). The disk was letting go---vehicle may even have been unable to drive (can't remember the sequence perfectly, but I already had new disks in the trunk). The other disk was relatively mildly cracked. After replacing both flex disks, the clunking sound was no longer evident. ALSO, now my 300E 4Matic is making a low frequency "rumbling" sound, starting at 40-45 mph (which condition originally was noted 500 miles ago as a "tick-tick-tick" sound---like a cell-phone on vibrate mode on a hard table, and occasionally like a half-wet bundle of spaghetti being slapped on a window) from the transmission shift lever area at 60-65 mph, where if touched, perceptible associated vibration could be felt. The front flex disk has one of its six inter-bolt sectors with a v-shaped derangement of fibers, flying outwards as a mini-Einstein coif. If I am dutiful, I will post a follow-up after replacing both flex disks (expect that they are of the same vintage, so the rear one is worth replacing even though cracks appear only minuscule and restricted to along the circumference of the six bolt washers, as observed from below the vehicle).