For the front most bolt , 14mm socket and 9/16 for the nut. You have to slide the wrench around until to feel it connect with the nut. It's that center bolt that seems impossible. Can't get your hands anywhere near it. Can't seem to get a wrench (9/16 wrench for nut, 9/16 socket on bolt)
near it. Barely any room to get a wrench there. Then there's the problem of replacing them with new gear in place. Please let me know if you find a solution. Do remove the deck and drive shaft belt guard. Better to have the mower raised off the ground.
PJDudley
P.s. I just now noticed that it might be that the PTO shaft and pulley might have to be removed. This would allow some room to get your hand(s) above the gear. I think that an impact wrench is called for to remove said shaft. Rrrrrrrrrrrh..!