Does the gear shift go into the 1st and 2nd positions? or is it jamming and wont move into the gate?
could be the Gate is out of Sync (Selector Rod detent is too week and the rod has moved half into gear (1 or 2) and the end of the gear stick is hitting the gate and not sliding into it (this was a common problem on older Zetors .... as i quickly found out on mine............... after a 2 hour ride on the back of the truck that delivered it, the 1st/Rev (on a 6745) selector had jiggled it's way all the way into 1st gear whilst the gear stick was already in 4th.
had to pull the gear stick housing off the top of the top plate of the gear box before i could drive (reverse) it off the back of the delivery truck! ...... much easier job with no cab fitted!
i fixed the problem with a stronger detent spring on the effected selector rod and have had no problem since.............. there are quite a few posts on this subject on this forum.
Other possibility is the selector fork is slipping on the selector shaft, (usually locked by a bolt on most gear boxes) in this case the gear stick will have full movement up and down the gate but feel very floppy between 1st and 2nd as the shaft is sliding in the fork and the fork is not pushing and pulling on the gears to select.
Worst case is you have lost all the teeth on 1st and 2nd but this is unlikely on a tractor .....(was very common on some cars! especially early 1980's Mitsi's .... and 1930's Ford V8's)
