I thought I would throw this out..98 Z71 Steering is "jumpy" only in slightly off camber situations. Changed idler and pitman arms plus tie rod ends and lower ball joints. Still have the problem Wheel will "jerk" or "dart". Turns out that in 97 GM went to electronic power steering. The trucks use a "vehicle steering sensor" for the variable part of the power steering. The sensor is located at the end of the column inside near the firewall. And is a fairly common failure part in 97-98-99 C/K series. My local dealer had the part for 68.00USD. Just a FYI...If anyone has any questions I have a schematic that I can send to them showing the location.