steering wheel hard shudder/shimmy

[dmac0923]

1995 explorer, when going over a relatively small bump at highway speeds it feels like the front end is loose and the steering wheel shakes violently.....it then settles down.

i crawled under the truck as it was getting dark tonight, and i couldnt see anything obvious.

i checked the following
lug nut torque
sway bar end links
outer tie rod ends
shocks

everything seems tight.

any ideas?
TIA

 

[daffy]

2 things come to mind: balljoints, and worn rack, balljoints being the first suspect.