That can get gummy and stiff. I use PB Blaster and the nozzle straw helps to shoot it in the pivot pin on top of the transaxle. If you wash your tractor down, or, if you store outside uncovered, water or rain water can find its way down there and combined with mowing dust it makes a bit of trouble. Keep hosing it with a proper rust busting lubricant and moving it by hand. A little heat (heat gun not a torch) can help to free it up. It should free up. This is not uncommon if you only freewheel it infrequently and it sits for extended periods without being moved to "neutral". Removing the transaxle is not that big of a deal on that mower; five bolts total plus the v-belt and then with the transaxle out, you can definitely get it all loosened back up. Its in an awkward spot to reach with pliers or a screw driver to try to move it.