Ford 2000 PTO Will Not Disengage

I have a '63 Ford 2000 4 Cylinder. Bought it last year with 106 original hours on it and use it as my primary tool on my small farm; now up to 190 hours. Have not had any major maintenance problems up until now, keep it lubed and PMCS before and after each use.

Two days ago I was tilling one of my market garden plots and the PTO would not engage and the shift lever would not move. I tried to remove the side inspection plate but it was stuck and the shifter crank had popped out of the spacer in the shifter shaft. I was able to wiggle it out with some effort and after doing so the the shifter shaft moved freely by hand when the clutch pedal was depressed.

I decided to remove and inspect the PTO shaft and everything there looked good, nothing bent, no indication of shavings and the tines on what I think is called the shaft coupling looked okay even though I could only inspect it from the rear of the reservoir with a flashlight.

I reseated the inspection plate and the shifter crank/lever and confirmed that it engaged the shifter shaft correctly. I reseated the PTO shaft and when I start the tractor the PTO is engaged as soon as I release the clutch, even with the shift lever all the way forward.

I removed the PTO shaft and started the tractor with the PTO shaft removed. Inspecting it from the rear I can see that the tines in the coupling link do not turn with the PTO disengaged (the lever all the way forward) and that they do spin once the lever is shifted to the rear (the PTO engaged setting). This would indicate to me that this is normal operating behavior.

However once I put the PTO shaft back in the PTO shaft is again engaged as soon as I release the clutch. I repeated the whole process again to see if I had missed something and again everything appeared to work correctly (if my logic is right) with the PTO shaft removed.

I am not a mechanic, just a fellow with a shop manual trying to puzzle through this. Any help with what I might be missing?

lots of guessing, but typically the rear shaft will get a slight twist on the splines from hitting something. This very slight twist is hard to see but really affects the operation. AND this twist is enough that when you put the shaft back in, it pushes the coupling forwards and engages it. AND this twist will can make it difficult to engage and disengage the pto coupler in normal use.

I would pull in inspect the pto shaft for the slightest of twist... any tiny twist will muck it up. Also inspect the coupler, and the foward shaft for twist or damage. The pto shifter needs to have good detents and the shoe needs to engage the coupler correctly.... MOST of the time, its a slight twist on the rear pto shaft and a new or used shaft will fix it. On the last tractor I was able to reach in and pull the coupler out and try to slide it back and forth on the pto shaft and could readily see/feel the problem, but it was a newer model. HOWEVER ymmv.

Thanks, I can't see any twist in the teeth on the shaft or any other damage, but I can't think of anything else. I will try a new shaft.