The short answer is - I take it all back. The steering wheel shaft does not move axially. The motion I thought I saw was just inaccuracy when using my eye to follow a mark on the shaft as the shaft turned. Today I wanted to get a solid measurement, thinking that would help in determining the thickness of the shim. On the end of the steering shaft near steering wheel, I used a tubing cutter to make a mark around the shaft and measured from that mark to the support the shaft passes through. I measured with a machinist's scale. As I turned the shaft I could not measure any axial movement. Next, I put a worm-screw type hose-clamp near the other end of the shaft, rigged a dial-indicator on a magnetic base on the steering box casting and took readings off the edge of the clamp. I got 0.014 inch movement over the 1/3 turn of play.