Break the tractor into and replace the ring gear.
ZaneThe best and easiest way to do this is to attach a chain hoist to the steering wheel at it's center and put a rolling floor jack under the clutch housing. Remove the caps from the radius rods at the front of the running boards. Remove the bolts from the steering sector where it bolts to the clutch housing. Remove any wires to the rear of the tractor such as tail or work lights. Remove the battery and the bolts that are around the circumference of the clutch housing. Tie a rope around the hood and the oil pan to help support some of the weight. I only did this occasionally did this but it just might be less stressful on the other stuff that will be hanging from the steering wheel.
Raise the chain hoist and the battery box will come above the clutch housing and allow it to clear when the rear of the tractor is rolled back. This is a good time to also check to be sure all the bolts in the auxillary transmission are tight because they are famous for falling off the front of the transmission when they get some age on them.
I would also check the clutch condition by removing the pressure plate and inspect it closely for broken springs or loose rivets holding the facing on. Also check the pilot bearing or bushing in the flywheel for wear. Always replace the throw out bearing.