Jd straight 450

I bought a John Deere straight 450 last year first gear only worked and the steering was slow and I finally got around to replacing the steering clutches and it's moved 5 ft after that and now I can't get it to move any at all I had the transmission cover off and couldn't see the synchronizers locking any gears together and not sure what is keeping it from moving when you put it in first gear the only one that would work it bogs the engine down and dies like there's two years locking together does anybody have any ideas