Right now im running stock emaxx tranny with alum input and alum output shaft,I do have supermaxx idlers, but im gonna put them in when i change to gmaxx single,after i do, it will be bullet proof, HOPEFULLY...

The press pins in the input shaft gears have been known to fail on occasion(usually after upgrading the rest of the drivetrain). There are a few ways to fix it, as mentioned in this post already. I usually replace the pin with a heavier pin and forget about it. I have never broken the pin twice(upgraded pins last and last). The stock Traxxas pins are pretty thin, actually. They weaken and break after a bit of high power running.

Well i broke my shaft pin today. I found that using a 2mm hex works well if you cut it with a dremel. Its a little hard to press in but it feels like it wont break or come out either.

You can also help prevent the initial breakage by supporting the stock press pin with a medium diameter body clip.