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

That sound exactly like my '81 300tdt with 152K.
I have no advice, just wanna hear what they tell you so I can fix mine too...
I'll let you be the guinea pig!

__________________
Current: '91 300TE 4MATIC 317k and climbing...
Former:
'81 300TD Wagon 168K "Tank"
'83 240D 216K 4spd manual "Da Bear" (aka best car ever)

"Never sweat the petty things...
and never pet the sweaty things."

... nothing yet?

__________________
Current: '91 300TE 4MATIC 317k and climbing...
Former:
'81 300TD Wagon 168K "Tank"
'83 240D 216K 4spd manual "Da Bear" (aka best car ever)

"Never sweat the petty things...
and never pet the sweaty things."

I discovered the hard way that replacing the center U-joint is a bad idea -- the 220 still vibrates.

The U-Joint is pressed in and straked -- no centering clips. They usually don't go bad, and also usually don't squeak. They sound like a bad muffler when bad, with vibration centered on the carrier bracket (check the floorpan beside the front seat -- if it is drumming, the u-joint is bad).

The good news is that some, at least, of your trouble is most likely the carrier bearing and rubber mount -- the bearing will grind or shriek when it is bad, and when the rubber mount goes bad, it allows the drive shaft to both thump and vibrate. You shouldn't be able to move the shaft in the carrier mount more than a just perceptible amount by hand -- if it shakes around, replace the mount and bearing.

You will have to completely remove the drive shaft -- pull back the center boot and loosen the clamp nut, mark the front and rear shafts for orientation so that you can get them EXACTLY back on the same spline, remove the bolts for the front and rear flex disks (mark both for location, they are balanced in place!) and the bolts that hold the carrier in place. Collapse the shaft toward the bearing and disconnect from the front flex disk, then the rear.

Plull the front section off, then I think there is a snap ring retaining the bearing. You may need a press to remove the bearing.

Press on the new bearing and carrier, put the halves back together -- you must install them EXACTLY as they were, even one spline off can cause them to vibrate -- not every time, perhaps, but who wants a car the drums? -- and re-install.

You may want to replace the flex disks and/or centering sleeves while you are in there.

You can check the u-joint while the shaft is out -- should move freely to all angles with no tight spots. If it is rough or binds, get a replacement -- used is fine if the u-joint is OK. They can be rebuilt (I can get the address, don't have it here) but that is about $600. The rebuild will have a serviceable joint -- the factory one is permantly lubed.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Peter: Thank you for your complete reply! I certainly hope it is the center bearing. There is another string that goes into some of what you have said, but your diagnostic advice is what I was missing. I will probably do the discs (and bolts)when in there doing the center bearing. Everyone emphasizes match marking the shaft, but you have put a finer point on it by emphasizing that I can't be off by a single spline. I will have to figure out how and where to place that precise a match mark on the junction point. Thanks again!

DJ,

Just a FYI, don't do like I did and find out the hard way... If it is starting to thump and shimmy, get it fixed now or you'll be replacing the whole shaft.

Mine started to squeal and after a couple of weeks, I finally realized what was making the noise. The next day it was starting to thump at low speeds. I made an appointment at the local MB garage to get the carrier bearing and flex discs replaced the next day.

The garage is about 40 miles away. By the time I got her there, the shaft was already damaged. At around $500 for a new shaft, I was lucky a friend had a used one. He dropped it off at the shop and got me back on the road!

Bottom line, don't delay or it may cost you $$$.

William: I appreciate your hard-won advice. I do not yet have a thump however, just the squeak, and then the ringing clunk I described at the start of this thread. I definitely have more play at the center bearing than Peter advises is acceptable. BTW I gather by"thump" you mean a repeated thumping, as if in time with rotation, and not the random clunk I described. Thanks.

Dennis:

Too bad MB doesn't do like Volvo and use a "missing spline" key on the two sections -- impossible to get it back wrong. They also use centering clips, so replacing the u-joints is easy.

Oh well, so it goes.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

While that squeal does sound like the center bearing, the "random clunk" sounds like what I had on my '84 300Dturbo (375,000 miles!). I pulled drive shaft and axles out to inspect only to find all was well. Clunk turned out to be caused by vacuum leaks that prevented proper shift modulation....do all of your vacuum driven systems work (door, fuel door, trunk locks, climate controls, brake assist, shut off)? I was certain it was a bad U joint or CV joint but it was just a vacuum leak! F

Fred: That is a fascinating idea. Yes I do have unresolved vacuum problems because my transmission shifting goes back and forth between smooth shifting and jerky shifting - sort of random except shifts are more consistently smooth with high rpm and hot engine. I did replace all the visible rubber vacuum lines and connectors under the hood but not the white plastic modulator valve yet. Also my A/C center dash vents do not work so I know that the vacuum driven valves are bad or something else in there. I guess I ought to get a vacuum tester and go through all that as well, although it also sounds like I have a center bearing problem. I have collected the materials to attack the center vents but don't have a tester yet so had put it off. Are testers easy to find? Also would you recommend simply replacing the white vaccuum control valve on top of the ip (I think it's about $35) ? Finally, I have no idea what the little in-line cylindrical plastic things are in the vacuum lines (they look like toy tops or pcv valves from a gas engine), whether they go bad, how you would know, or what to order to replace them . Thanks for the idea!

Hi Dennis:
Check my prevoius posts and photos about tackling your center vent problem. I had no vacuum too so I improvized bu applying suction with mouth. But getting a vac tester like Mity Vac is not a bad Idea. Mity Vac has a model called silver line. which can also be used for you future break bleeding projects. Check their website for details.
Next to your Q
"Finally, I have no idea what the little in-line cylindrical plastic things are in the vacuum lines (they look like toy tops or pcv valves from a gas engine), whether they go bad, how you would know, or what to order to replace them"

Well those little thingy are check valves. They are sometimes, Green, yellow etc. color coded. They as far as I know prevents back check( thst is they allow the vacuum to travel in a one paticular direction) Again to test them you apply vacuum on them from one direction. and see if it sucks in air, then try applying vacuum on othe end and they will hold the vacuum.

The occasional clunck is my problem too and I am trying to trouble shoot it too. I am not too good with Tranny. My center bearing has a little play and the rubber mount looks old and has started cracking so I will have it replaced along with my leaking differntial oil seal( Pinion seal). Flex plate too can give clunck if they are loose or if the holed in them have developed a play over a period of time. To check the flex plates, hold propeller on each side of flex plate in question. and twis them in opposite direction( you will have to twist is very hard) If there is a play you have a problem at that flex plate. If no play that flex plate is good.

Hope this helps.

MVK

__________________
One penny saved is three penny earned.

1985 300D Turbo 179,000miles