Massive THUD from passenger's rear wheel

I have a '81 300TD wagon.

In summer I replaced the nitrogen cells and rear sway bar links with an immediate improvement in the ride. In August, when I checked, the SLS was working great.

Now, over the last few months I'm experiencing a really, really massive THUD with even relatively small bumps. It seems to be isolated to the passenger's rear corner of the car.

I've checked fitment of the doors, and checked to make sure that the jack/ tool kit are secured.

Anybody else out there with this experience?

[psfred]

Check the lower bushing on the strut and the connections to the swaybar, also the swaybar to frame bushings. Check for a loose spare tire, too, even though it's on the other side.

Peter

[luckys420]

what about the rear subframe bushing? Check that as well.

[phidauex]

I get an occasional 'thock' sound from my passenger side rear strut, due to a little bit of air being inside of it. The system is supposedly self-bleeding, and when I disconnected the linkage on the self-leveling valve and moved it up and down a bunch, raising and lowering the rear end, the sound almost completely went away, though I hear it a little bit on big bumps.

I'd check your self leveling fluid level, and look for leaks on the strut. In addition to the other fine suggestions.

peace,
sam