Warden,

I guess I'll be the one to say I told you so

The guide rod is a ball joint at the back end. It doesn't look like the spring has to come off on a W126. The W123 set-up is similar.

When they get really bad you'll feel a clunk as the car shifts forward relative to the guide rod when you slow down. My 81 SD was that way on the right side.

I don't know if worn guide rods will account for loose steering. AFAIK they're mostly to keep the wheels in place when braking. If the steering is loose at a stop of constant speed, I'd look for something other than the guide rods.

Have you checked that the bolts that hold the steering box to the frame are tight? Don't move them as they have some sort of thread lock on them. You might upset the thread lock is you give them anything of a turn. I think the manual says they shouldn't be reused but maybe they can be reused with Loktite.

Sixto
91 300SE
87 300SDL
83 300SD