Posted by JDEM on March 22, 2020 at 12:41:21 from (47.33.231.52):
This is an update RE my NAA Jubilee. As posted earlier, I thought it was a simple gear-drive tractor. Problem was slippage between the engine and rear wheels. I thought at first it just needed a simple clutch job. NOPE. I found out the hard way this thing has a kind of rare optional "live PTO" package added, likely by a Ford dealer. I find it odd that Ford would try to install a hydraulic clutch pack at the output of the transmission where there is little gear reduction. It takes a lot of clutch at that point if intended to last and not slip.
I posted several times here since even the Ford tech manual did not show all the internal parts or describe how this thing is supposed to work - other then simple general comments.
Now I know since I just got done taking it all apart to the last nuts and bolt.
It is a well built and kind of interesting design. Theory of operation is like this. THIS is the info that should of been in the Ford tech manual. When you start the engine and the PTO pump turns, there is low pressure fed to the clutch pack if in "disengaged" position. This low pressure over-rides a stack of springs and unlocks an all steel locking plate. So just to make things clear. When the engine is shut off, and the PTO pump stops turning, metal Belleville Washer type springs force a steel lockplate into place and this locks up the entire clutch pack. Ford did this so when the tractor is parked and left in gear, it would not roll away. When you start the engine and put the control lever in "engage" or "lock" position, high pressure oil forces a piston against the 8 clutch facings and 8 clutch steel plates and makes the pack lock up under hydraulic pressure. So, there are three different modes of operation. #1 is PTO pump not turning and all steel lock up. #2 is PTO pump turning and low pressure to over-ride the steel lock-up but not enough to lock up the clutch disks and plates. #3 is PTO pump is turning, and high pressure is sent to the clutch pack and the clutches engage.
So, now I know. I found nothing wrong with any parts except worn clutch facings. The insides of the tiny PTO pump look like new. There is, however, a major part missing. There is supposed to be an accumulator to soften the clutch engagement. I assume it blew once upon a time and someone split the tractor, removed it, and blocked off the oil feed to it.
I have the tractor split and bought a long splined driveshaft coupler that is what the NAA Jubilee had originally before any PTO kit was added.
What I did not know is this. Seems if I had just removed the PTO pump entirely, that tractor would of gone into a permanent lockup mode and worked fine. I.e., once that optional clutch pack goes into the all-steel lockup mode due to no oil being delivered, it acts just like it has a solid steel coupler (like I am putting in now).
Yes, a long winded post. Might be of value though to someone else who has this sort of trouble. I searched around a lot and was unable to get this detailed info anywhere.
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