Underneath the floor pan you will find a roller that rides in a v shaped plate. This is the forward/reverse/neutral system for your tractor. Things get jammed in it. The roller comes off the plate etc.
there is an eccentric bolt adjustment on the left side accessible from the side. There is also a bolt that secures one arm that may come loose. Access through filter cover removable. And, as you will see, a spring that may have come off.