Tractor Repair: 4310 JD transmission stuck in gear, shift linkage, forward position

Question
I have a 2001 4310 - the four speed transmission is stuck in (second) gear. I have had problems with the shifting finger breaking off and thought that might be the case again but when I pulled the side cover off the weld is still in place and the finger was still engaged in the shift rails.  The upper (3/4) rails that move the shifting forks will move back and forth smoothly for a short distance so are not totally frozen, but it appears the lower one (1/2) is stuck in the forward position. Upper one is in neutral. I applied persuasion to the lower rail and while the rail will move (something flexing) it does not want to pop free. Detent stuck somewhere or something stuck inside. Any ideas? Thanks.

Answer
Wow, Tom, this question is tough......I am thinking that there is something is impeding the rails....and it could be anything. Piece of metal, or something of that nature binding up the works. You might be able to pop it out of gear by starting it, popping the clutch and trying to shift into neutral while you do it....it MAY work....and make sure your shift linkage is working properly. But. An internal trans problem, especially binding, is pretty serious, so the bad news is that you might have to break the tractor apart to get in there for a close look. Wish I had a better answer for you. Good luck!