Aldot did it by assembling the clutches on the axle (including tightening the nuts properly) then holding the two ends of the axle in his hands so it couldn't rotate. He rolled the pulleys (on the outside of the clutch disks) back and forth across the bench. By feeling how hard the axle was trying to rotate, he could monitor the drag. No drag, take out a shim. Too much drag, add a shim. Not too difficult, I think, once you have the axle out of the tractor.
