Once my car warms up completely and I come to a stop light, when I am sitting still I hear a clunking noise, seemingly from the rear end or drive shaft, but also an increasingly rough idle in the engine, with speed matching the rear end clunk. If I put it in neutral or park, the clunking gets much louder, so much so that I avoid using P or N except to turn the car off quickly.

When I arrive home, if I look under the car, when in P, I can see the drive shaft moving back and forth, in time with the clunk! It rotates maybe 10 degrees clockwise (a guess) then the same the other way, back and forth, clunking away until I put it in drive. Now why on earth would it do that?? I searched the posts and didn't see anyone else with this problem. The car basically drives fine, does well on the highway. It does have a couple other nuisances developing, such as I have to start it in N instead of P. Also, around 1200 rpm there's a scraping noise coming from below the shifter, related or not...

The scraping at 1200 rpm is consistent but the clunking is not, like I said, it only does it when the car is hot and idling but sometimes it doesn't do it at all. Doesn't seem to depend on how fast I stop. But I'm convinced that all the racket is coming from the drive shaft rotating back and forth. Anyone seen this? Do I need a new transmission or differential or just to turn a bolt? Thanks!

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Orion Parrott

300SD 1982 202k
300TD 1987 275k
Suburban 1987 6.2D 4x4 156k
200D 1967 gone but not forgotten
380SE 1985 gone