re the speed changer shaft, it is quite worn, someone in it's past did not believe in lubrication. :eek:
However, I would not give up on it just yet. The two outer sheaves are fixed and the center sheave should only slide back and forth, not be spinning on the shaft. I would try cleaning and polishing the shaft (and lubricating), and then see how it works.
Mine had some corrosion, I polished it using the lathe function. :)
https://www.shopsmith.com/ss_forum/viewtopic.php?p=232776#p232776