The 'wandering at speed' problem is often balljoints.
Knocking or groaning noises when going over bumps at low speed also points towards balljoints.
Shimmy alone is often play in the rack (if not wheel balance, tire problems, etc.), such as idler arm bushings, any of the many tie-rods.
Here is how you check balljoints:
1) Place jack under control arm (as near to balljoint as possible) on suspect side, and lift until tire is about 3 inches off ground.
2) Make sure jack is really secure!
3) Grasp tire at 12 and 6 o'clock, and attempt to rock inwards and outwards. If there is any play, have an assistant observe the balljoint to verify the source (could also be the bearing).
Now check for play in the rack:
1) Grasp tire at 9 and 3 o'clock, then rock left and right.
2) Should be no play.
I have observed that the balljoint on the right side seems to fail first, and the idler arm bushings (also on the right) are short-lived, so suggest starting on the right.
1986 300E 5-Speed 240k mi.
Last edited by csnow; 06-21-2002 at 04:37 PM.