The vertical movement on the driver's side indicates there's probably something amiss.
I'm pretty sure that there are a couple of gear designs, but most have a spring-loaded nylon cup that pushes the rack onto the pinion (stabilizing the vertical movement). There may be a screw adjustment or shims to adjust the pressure. Pull the cover plate off to see how things work. I don't think that there is a replaceable rack bushing on the driver's side.
