I get a random ringing clunk from my 81 300TD in lulls between transmission shift transitions usually at low speed down shifts. I also get an occasional high ringing sustained squeak from the center bearing area that I hear only at low speeds with the window open - reflecting off the curbs and cars in a tight street. The clunk sounds and feels exactly like bad u-joints that I could easily fix in the various early 50s chevies I used to have as a kid. The ringing squeak sounds a little like a wheel bearing but the fronts were recently packed, and it does not have the wowing sound I associate with that. Inspection shows only that I have about 1/8 inch play at most in the shaft at the center bearing. The U-joint looks solid as a rock but who knows? I have 178K on the car and the drive shaft has never been touched although I did a half shaft to cure a rotating deceleration clunk there. Do my symptoms sound familar to anyone? I particularly am interested to know how much (if any ) play/movement is acceptable for the driveshaft at the centerbearing support, and whether the U-joint can be lubed/serviced. I have seen some postings that suggest that it can, but I can see no zirc fittings - so does one disassemble it and repack it? Thanks