Bobcat B300 Shifting problems

Hey my uncle has a Bobcat B300 that ill be taking to my Diesel class to work on next week and i'm hoping to get some advice on what it might be before we start. It starts up fine. when we try to shift it into FWD or REV it wont budge. It has a hydro-stat. transmission. I am thinking maybe the shift handle might have loosened or something. or is it the hydro-stat. drive motor? im an novice mechanic and would certainly appreciate any advice on what it might be.

Bobcat B300 Shifting problems