Ok, I looked at a few posts on here that cover steering and front suspension, but I am still not exactly sure what I need to adjust/replace to get rid of this steering shimmy (side-to-side steering wheel vibration) that shows up from time to time. If it happens, it only happens between speeds of about 50 and 60 mph, and it seems to depend on the kind of road surface I'm on. If I accelerate past 65, I never see this vibration. And like I said it's sort of intermittent.

Here's what I checked and/or repaired so far on front suspension/steering:

- all front wheel bearings have been replaced

- upper control arms have not been replaced but balljoints on them don't have any play so far. bushings on control arms are still tight.

- lower balljoints on both sides have been replaced (by the dealer)

- guide rod mounts (aka castor sockets) have been replaced (by the dealer)

- steering shock has been replaced (old one was pretty much spent, but it didn't make much difference)

- large bushings inside the L-shaped "bearing" that's mounted next to guide rods (subframe bushings??) have been replaced

- alignment has been done (by the dealer)

I have NOT replaced any tie rod ends, the center draglink, or the steering coupling. Lower control arm bushings have not been replaced, but visual inspection was satisfactory.

Are there some suspension/steering components I am overlooking? What could be causing this steering shimmy at resonant speed that I indicated, and with all the things that have already been replaced?

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84 300SD - bought in April '06 with 237,000 mi