Clunk when going approx. 2-3 mph. Driveshalft problem?
 

Two days ago, my 1968 W108 280S started making a clunking sound in the rear end when going approximately 2-3 mph (whether in forward or reverse). The sound is similar to a cow bell. Today, I also felt some very slight vibrations when going 30-40 mph.

I think I have eliminated the possibility of items rolling around in my trunk or a loose muffler/exhaust. Is this a potential driveshaft problem similar to what is discused in the below thread?

http://www.peachparts.com/shopforum/vintage-mercedes/205055-what-happens-when-you-ignore-little-driveline-vibration-2.html

Any thoughts are appreciated.

CNM

Update after my commute home: The clunking noise stayed the same. However, the vibrations around 20-40 mph increased dramatically on the way home (pretty damn loud). I am thinking I may have a busted u-joint. The car made it home with no major incident, where it shall stay until I figure it out or get it to my mechanic. However, if anyone has any thoughts, let me know.

I'd check rear flex disc as well as trunk-mounted diff bushing.

i think this car has U-joints front and rear. I had a 1971 109 and it still had U-joints.

It could be those, but I bet it is your carrier bearing. When these go they normally freeze up tight and then tear out the bearing carrier.

But if you are in there replacing the bearing you are nuts not to replace the carrier at the same time. On newer Mercedes there are a one-piece part and replacements for your car may also be a one-piece by now.

The only way to tell is to crawl under there and start shaking things around. The U-Joints should be nice and tight with NO slack or play. Push up the driveshaft in the middle and see if it has any axial play. If so you will need to replace the carrier bearing as well.

Be careful when taking off the driveshaft. They are balanced as a unit and the little weights can get knocked off rather easily. These were supposed to have been tack welded on at the factory, and maybe they were, but I have knocked them off and used superglue to put them back on and never had a problem with them coming off later.

Just be sure to mark the driveshaft so it is reassembled the same way it came out.

Some larger cities have shops that can balance two-piece driveshafts, and if you have to remove it then it might be wise to have it rebalanced before putting it back into the car.

A cow bell sound at that speed to me means you have a lug nut off rattling inside a hubcap. This _maybe_ could cause a slight out of balance feel at higher speeds but I kind of doubt that... If not that, look at recent vintage thread on Benzworld about clunk in 230S and older thread about clunk in 108 (outer axle bearing)

Not one but two actually (back left tire). Tightened them up Tuesday, double checked all other lug nuts, and the W108 is driving back to normal. I suppose this was a by product of not tightening them well enough a few weeks back when I bled the brakes. When I was under the car, there did not seem to be any issue with the ujoint. However, I did notice a busted o-ring gasket near the differential. Picture to follow.

Not sure what this is, but appears to be a busted gasket near the differential:

http://img820.imageshack.us/img820/3707/photolnl.jpg

However, the car is still driving fine today with no clunks or vibrations.

Yahoo! Score 1 for a REALLY easy fix. Happy your cow bell has gone away, and particularly without a wheel falling off in the process...