Has anyone experienced the following symptoms ? Know what is causing it ?

Problem :
My 1990 240 with 194,000 miles has developed a front end rattle/wobble felt thru the steering wheel , when making gradual left or right hand turns at 45 mph or more.It makes no wobbles when making anything greater than 45 degree turn. iIt makes no wobbles when turning at lower speeds than this . It makes no wobbles at any high speed ( 80 mph ) or when going straight even over bumps .

The Car :
No detectable play in any of the steering components ( tie rods , rack, ball joints ) . Outer tie rod ends have been replaced . Shocks , rack and ball joints are likely the originals . Rubber front end components are pretty dreid out but other than the occasional clunk seem to be ok.

Conjecture :
My last 240 started doing this at about the same mileage , so this must be a common problem ? ( but I sold it before I ever figured out what was going on )

I suspect that it is caused by a little play in a lot of components , so may be something that I'll should learn to live with ?

Thanks for any odeas where to look with this ...

Todd