What I have found in the few that I have dissassembled (both cars and trucks) is that the bearing surface on the worm shaft is damaged. Generally the upper bearing runs out of grease and wipes out the bearing and the shaft becomes badly pitted. This surface is hard chrome and could be redone or the shaft replaced. There are kits available with bearings and small parts and the book gives a good rebuild procedure. There are a couple of sources in my area that do a good job rebuilding steering boxes and are reasonable.
Fred


1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine