That's a bit unusual, usually an upshift is easier on the snycros than a down shift.

Replacing the snycros involves pulling the transmission apart about as far as it can go. It's not an impossible task, but it's just not like taking a motor apart. You'll need some very heavy duty snap ring pliers (with flat serrated jaws, not pins) to take off a really big snap ring. And a very good guide on how the pieces fit together. There is a very good article on Vlassics.com.

My otherwise fine junkyard M41 that I put in my PV had totally non-functional syncros on 1 and 3. I put up with it for most of a year before taking it apart and putting in the syncros from my M40. Spent a couple of evenings trying to reassemble it, but that was mostly due to my attempt to mix and match the best looking gears from the two transmissions based on a casual look and an assumption they were the same. They weren't. But the syncros from an early (63) M40 had the same part numbers and fit perfectly into my late model J-type M41.
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