But the theeth that mesh between the layshaft and mainshaft gears still don't have anything to do with the collars that slide past the syncro blocker rings and engage the dogs on the mainshaft gears that lock them to the mainshaft and put it in a 'gear'.

When I first put a junkyard M41 in my PV, I found thatit has no syncro action on first and third *at all*, regardless of temp. A while later, when I finally got around to pulling it again to fix it, I found the #1 syncro cracked in 2 places, and the #3 in one place. Swapped them with the syncro rings out of my original M40 and now it works perfectly.
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'63 PV544 rat rod, '93 Classic #1141 245 +t