My Sears Craftsman 11hp Lawn Tractor Model #917 254 270 :when engine is running and clutch is disengaged,it will not shift to another gear. You have to turn it off and move tractor back and forth before it will shift into another gear. Any ideas what's causing this and what to do about it? Or, is the gear box just worn out?

Just needs to be topped up with some gear oil take the rear end off the tractor and remove the pully there will be a square bolt, take it out and fill up with lawnmower gear oil

This rear end has grease in it.
Sounds like maybe the brake needs adjusted.sounds like the transmission pulley isn't stopping,
This would make it hard to shift.

Could be the rod in the rear end is slipping off the connecting rod, and would have to be taken apart to see if it is off the connecting rod, that would cause it hard to shift