Ted Talbert,
I am not familiar with knee action shocks. My uneducated guess is that they should offer resistance in both directions similar to a modern shock.
If a steering component is loose or worn, play would be felt in the steering wheel and the truck might have a tendency to wander around.
It's my feeling that a shaking or vibration has to come from a out of balance rotating mass.
A vibration isn't the same as bouncing. The engine could produce a vibration and transmit it through the cab to the steering column.
If all front end components are relatively new, and are adjusted properly...this includes the steering box and wheel bearings, I would still suspect the tires.
Stuart
