2002 TC40S 12X12 four speed lever on the dash, heavy shifter resistance when attempting to shift gears

[nickel plate]

"S" for standard 12X12 transmission. Problem is that the four-speed right dash mounted shift lever, first, second, third and fourth gear changes are VERY stiff, scary stiff so I generally leave it in one gear position and deal with it.
A couple of years ago I had the shuttle shift forward and reverse linkage break down (easy fix) on the other side (left) below the dash so I'm familiar as to how to get to at least the linkage train. So before I remove the right-side lower panel below the dash, any advice as to how correct this problem?