My 1983 300SD with 350,000 miles tends to "wander" / weave from side to side at highway speed when on a stretch of road that has grooves (running paralel to the road).
Would the cause be most likely a worn out steering gearbox or the idle arm bushing (or both). I had difficulties before trying to adjust the nut on top op the steering gearbox and finally settled on what was tolerable because I could not achieve ideal.
I replaced the steering shock absorber 3 years ago.
Any thoughts? Thanks, Dieter