Yanmar 3GM30 KM2P transmission problems

[thebeaners]

I have a KM2P transmission, it started to slip a couple of years ago. So I thought the cone clutch was worn and replaced it. The new one looked exactly like the old one so I don't think it was worn. Now the transmission is noisy now and still slipping. I think part of the problem is in the shift arm. It shifts into reverse with only a small travel of the arm from neutral. For forward the shift arm has to move all the way to the stop and then just barely makes the output shaft turn. It looks to me like the forward lever position bottoms out at the same time it engages. This is right on the transmission, nothing to do with cables or linkage. What I would like to try is to shim the cone and cup gears further along the shaft. Which would move neutral position closer to forward, this should make it shift into forward and have some overthrow left. From what I read and experience of others, rebuilding a transmission is a lost cause, just buy a new one. I have about 3000 hours on the engine.