F4 and F4i transmission/tranny swappable?

I would think not, but I always see the F4 and F4i listed together. I've heard the complete engines are swappable, but I wasn't sure about the internals.

I'm having the problem where it slips out of 2nd gear, so I'm guessing the tranny needs to be fixed/replaced. Any advice?

You can replace the gear. The tranny is a single unit with the engine for Jap I-4's

Thanks. I was just wondering in case I had to replace the shift forks and/or shift drum too. I'm sure the best bet is to just get F4 parts, but I've seen a lot of F4i stuff for sale.