I had something similar happen to me on my SM420 4 speed. Mine kept popping out of 4th gear. It turned out that the roller type pilot bushing (bearing) came apart and the clutch gear wasn't properly supported and created a miss-alignment. Replacing the pilot bushing with a solid brass bushing solved the problem. I will not longer use the roller bearing type pilot bushings for this reason.

Last edited by 54Belair; 06/12/2026 1:50 PM.