Steering coupler question

The stock steering shaft is not solid, the lower solid portion telescopes inside an upper tube. The only thing holding it in place is a pair of nylon shear pins which usually break loose as soon as you disassamble the column, or at least they did on mine. The u-joint is bolted to the lower shaft and the set screw retains it on the steering box spline. Any up and down movement simply moves the solid shaft inside the upper tube.