Update - I removed the big lock-nutted screw and, as you suspected, the lower bearing had not been installed correctly and was out place and somewhat deformed. Once the new one is received and installed I am hopeful the issue will be resolved. In playing with it a little, the shaft moves up and down smoothly when pittman arm is attached and providing resistance; when disconnected and end screw lightly in place to capture the shaft, there is no up and down and the pittman arm moves freely/smoothly. Thanks for your help!
In response to your earlier questions - yes, the shaft inside the column/mast is what was moving up and down (wheel is removed). My assembly manual is 55-59 but really only 55-57; my shop manual is specific to 1958 and reflects minor changes made that year.
