Driveline or Bad Tires?
 

Recently, after prolonged driving, my '84 300D developed a clunking noise in the rear which became much louder (and slower) when I slowed down, suggesting that it was vehicle speed-related. The first time it happened during a long trip, I suspected that the heated-up tires were the culprit, so I had my tires rotated and balanced. This resulted in a severe vibration in the front--a predictable consequence of putting a bad tire on the front that had been in the rear. So I replaced the bad tires (now in the front, with the presumably good tires in the rear) with a couple of Yokohama's...a superior tire. This seemed to remedy the noise and vibration until today, when I took another long trip, and the same noise arose from the rear. The noise didn't become audible until I had driven at speed for about an hour, and then had to slow down for city driving. Can I reasonably suspect that ALL the old tires are prone to develop this same characteristic? By the way, the old tires are Pirelli's, a brand that I'll never again consider. This might sound as if it should be in the tire forum, but I'm not totally convinced it's tire-related.

I jacked up the rear and looked for play along the axle shafts, and other obvious things. Everything seemed normal. Does this sound as if it's definitely the tires? The reason I have ANY doubts that the tires are the cause, is because the clunking noise sounds so much like metal driveline instead of rubber...

...any ideas?

Thanks Bill. That's about what I suspected...and feared.

Matt

I had this happen to my 240-an awful clanking noise from the rear happened after I had pulled a U-turn...:confused:

I pulled another U-turn in the other direction and it went away!

Was a CV joint giving up. Replaced both with junk yard ones.
Look for new rubber boots for a recent replacement.:D

Completely Unrelated!!!
 

But the symptoms sound identical!!! Numerous times on past vehicles and most recently on a GM frontwheel drive box these symptoms have been indicative of constant velicity joint failure. Doesn't your car's rear axles employ a couple of these joints. Wheel speed related noise gets much worse quickly over time. Slow turns are the worst. Just a thought, Good luck.

Matt, BillyBob

When I looked under my 240D, I couldn't see anything obvious, and the axle shafts looked normal.
I jacked up the rear of the car and supported the body on jack stands (not under the axles, of course) and ran the engine in drive (D). I could easily tell it was the CV joints.
Replaced both axles with junk yard ones.
Each axle comes with 2 CV joints.
When I got them off the car (refer to Haynes manual for removal) I could tell which one was bad by turning it in my hand.
I did a search on this forum concerning "CV joints" and it helped a lot.
Not cheap new...