Its been a while but there's a bearing toward the steering wheel that keeps the shaft straight by the wheel, and then there's a plastic bearing at the end of the housing that centers the tube. when its mounted to the steering box it usually centers itself in the tube.

I did take a piece of foam (from the heater box piping) and slid it into the tube over the shaft. I pushed it in far enough to be flush but keep dirt out.

Hope that helps.

Scott