[DRobinson]

It could be as simple as the pin on the shaft at the bottom of the lever is broken. The 2010 was not JD'a best effort in tractor building. It has been a long time, but my guess is that you will have to remove the rockshaft housing in order to see the linkage from the bottom of the lever to the rest of the linkage. If the owner is correct that it worked and then just quit, it is probably something simple, but not easy to get out. If you can get a John Deere technical manual, it will help you immensely with this repair and future repairs.

If Tex Jim sees your post he may have a better idea.

 

[DRobinson]

If I'm not mistaken, the tractors above serial number 42000 were much improved over the first ones. On the shift lever quadrant, are the gears 1-2, 3-4, 5-6, 7-8 or 1-3, 2-5, 4-7, 6-8? I believe that changed at serial number 42000 also.

When I suggested getting a Tech Manual, make sure you get a John Deere manual and not one published by some other publisher.