Just finished HARD plowing 12+ acres. With a $400 tractor

The 9N is older than the 8N
8N and 9N have the same sort of PTO. It is not live. A lever turns it on or off and it is dependent on the clutch.There is a chance of the equipments spinning momentum making the tractor continue forward even if you have the clutch disengaged.
This can be remedied by using an overrunning clutch on the PTO shaft which will allow the equipment to spin down without affecting the movement of the rear wheels.

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Deja Moo; The feeling I've heard this bull before.

I think this is true of all the old tractors nearly. I think what helps other makes of tractors is that they have way more weight and horsepower. Ive had it happen with me with my H till I got an overriding clutch.