I have put new bearings and seals, and synchro rings from no so much wear into a broken 5 speed transmission from a 1998 maxima I picked up earlier. It is in my 99 SE and running fine thanks to advice I received from CS_AR. I had trouble starting the engine after the transmission install, which turned out to be bad ground.
Any way, the original transmission which I thought would be in better shape had some damage in the main shaft gear. I see several teeth with damage as seen in the picture. I do not need a second transmission, so I do not want to spend too much money to build this one. If I can repair or replace the broken main shaft, I want to go ahead and build it as its synchros are in good shape, and I have a brand new set of bearings and seals already.
Is there a way to repair this type of damage reliably? Or is it better to find a used main shaft?
Do I need to find a main shaft from 4th gen and 5 gen with 3.0 engine, or will a 3rd gen main shaft also work?

 

Sorry that I have no experience in this area.

I would call https://www.courtesyparts.com/ as ask if they have someone who can give some answers. Other than that, I would try to find another used transmission to scavenge parts. I think Atlanta is one of the best locations to find salvage yard parts for Nissans.