I don't know how old your tractor is but anywhere a shaft goes through the trans case is suseptable to rusting and getting stiff. As mentioned, WD40, PB Blaster, or some sort of loosening oil is good to get it going. Then the white lithium to keep it there. This happened to me after my first Winter plowing. HST pedal, range selector, brakes, 3pt, all became stiff. Once loosened as mentioned, I use white lithium Spring and Winter. Good for 9 years now.