Tips for Rebuilding the FS5R30A

I know this thread hasnt been active for years, but any help from anyone with experience with the FS5R30A would be greatly appreciated.

I have a Nissan Frontier 2005 2.5L Rwd with the same transmission. It started to pop out of 2nd. When I took the off the outer case, the fluid was muddy brown and a spread spring from the 3rd and 4th synchro hub was broken. Im looking at the teeth of the 2nd main gear and they are fine. When moving the gears around, second gear had substantially more play in it. I dont own a feeler guage so i used paper. Going by how paper is 0.01mm thick, it felt tiight but using 4 sheets thick of paper, it still fit.5 sheets is too thick. I know its inaccurate but it still places the play at arround 0.04mm when it should be around 0.02"something" to 0.033 mm. What would wear out to cause this play ?Any ideas about what is causing it to pop out of 2nd ? The shifting forks look fine. Will replacing the synchros fix it? I plan on getting feeler guages in the morning to check the play again. Im concerned i might need a new 2nd gear. The dog teeth look fine though.
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