Is that one of the marlin HD bearings?
Yea its the sealed type bearing he uses to eliminate the weaker stock input and output bearings. They are large so the holes had to be enlarged. Its part of what makes these HD stronger.
I'm of no help.... Can you tell what and why about what cause the failure yet?
I cant say for sure but one odd thing happened when I was tearing it down this far. The front counter shaft bearing is suppose to be pulled just like the main shaft but it came out very easy. I am almost thinking that if that bearing wasnt tight enough it would have allowed that shaft to move when it shouldnt have. Tho the bearing looks perfect on the inside. Im gonna need a new counter shaft anyways so that should resolve it.
I have a large press here and decided I am gonna use it to push the main shaft thru the case little by little. Sucks that the gears I need to get to are on the very bottom.
I wont know anything for sure till I get it completely apart. If I cant get it apart safely then I am just gonna stick this trans aside and give up on it till I can afford the right tools to do the job. Really not fond of running this L43 since freeway rpms are way to high for my liking. 3800 rpm to do 70.