[Gromit]

Not sure this will help except in a preventative way; but regarding any hammering on the shift lever please keep in mind the forces translate through the linkage into the linkage bushings and the mechanism that moves the valves to and fro in the transmission valve body.

On my 1970 shift lever the bore for the pin was worn enough that a roll pin would go in with moderate resistance. So for example I didn't disconnect the linkage from the trans as a precaution before installing it. After installing the shift lever roll pin I put a machine screw (sorry; don't know the size it may have even been metric) into the top of the roll pin and that expanded the roll pin just enough to stay fast and without stressing the linkage and transmission controls.