Put your bucket down firmly to stabilize the front of the tractor...
If you can safely get both rear wheels jacked up off the ground with a LARGE floor jack with wheels, placed in the center of the tractor, and going in from the side, you likely can:
1. Lock the parking brake so the front wheels don't move,
2. Gently, but firmly push the rear end back in a straight line so it is not articulated. You should be able to compress one steering cylinder and extend the other, by pushing -- with no builtup pressure in the hydraulic system...
Note that you need to hook up the bypass hose before you try to push the PT and have the wheelmotors turn...