I wonder what the problem is
![Head Scratch :headscratch:](https://board.marlincrawler.com/Smileys/marlin/headscratch.gif)
... So out it comes from the main bearing. Low and behold the 1/4" thrust washer ball bearing is preventing the shaft from sliding all the way in the main bearing. (I think the main shaft ball bearing seat was machined in the wrong spot, apparently 0.040" off.) A little grinding and I made the ball bearing look like a 65% pie. This allows the new main shaft to slide in enough for the hd snap ring to seat in the output end of the shaft, still keeps the thrust washer from moving around too much, and still has a little bit of play to it.