L245DT 3PT Problem

I recently bought a L245DT circa 1977. The seller told me the 3pt hitch had worked until recently but the control lever “went bad”. It was flopping around uselessly but everything else was good. I drove it around, used the FEL and drove it a mile back to my house. It was there that I discovered that the 3pt speed control (below the seat) was locked tight. I loosened it and the 3 pt hitch worked! I tightened the lock nuts on the lever control to get some friction and hold the lever in place. Not sure if it means anything but I found the hydraulic fluid very high, I drained at least a gallon out before it slowed down at the check hole. Everything worked for a few days until I put my brush mower on the hitch and dropped it down (too hard perhaps) and then nothing. The 3pt hitch wouldn’t pick up the mower no matter what I did.
Finally I took off the seat, uncracked the eight (or so) nuts and bolts holding the top of the rear transaxle down and managed to lift it clear. Under the top of the case the rod (the lever spool drive according to parts list) that connects the lever control to the control mechanism (attached to the left 3pt arm) on the other side of the case was missing. I found it in the bottom of case under the gears and all that oil. I put it back in place, replaced the oil and screen, reassembled everything and it all now works. But here’s the question… why did it fall off in the first place? Did the 3pt arms extend too far down when I dropped the implement? Is the control gizmo attached to the 3pt arm, out of adjustment? Is the linkage attaching the main valve control to the spool drive rod (the part that fell off), out of adjustment? Should I be tightening the nuts on the 3pt lever to get friction or should there be a detent in the system? I have a shop manual that under-describes everything and is not much help. I’d appreciate any advice.

Well, weirdly this thread has been revived just as the problem reappeared...
Yesterday, six weeks or so after the original problem I was moving manure with my loader and generally wrestling in the mud. I dropped the box scraper to scrape out a path, it fell pretty hard. and then nothing, the 3pt lever went useless.
I'm pretty sure the "lever spool drive" (which connects the control lever to the position control valve and extends to the relief valve) has fallen off again and dropped into the sump.
I know how to fix it now but still haven't figured out why it's happened. When I get it apart I will go over all the parts again and make sure everything's accounted for.

I managed to get the box scraper off and get the tractor back to the barn. I'll pull the rock shaft off the sump, find the pieces and take some pics later today. But when I had it apart before I didn't find anything missing using the parts list or the WSM.
I was also thinking that the feedback control was out of whack. I'll look for circlips as well.
Thanks.

Okay, my assumption that the lever spool drive that had come off before had come off again was wrong! I removed the rock housing cover, flipped it over, and the position control valve and all the spool levers were in the proper places. But as I was taking it apart I realized that the 3pt arms had no tension on them... and the piston wasn't falling back to it's lowest position inside the cylinder. I took the cylinder cover off and everything inside looks pretty good. The cylinder and piston are both smooth, unworn, and no rust, but the piston was stuck at the top of the cylinder. So... I guess maybe the position control valve has somehow failed.
I'm going to study the WSM and search this site and try and figure that out. It seems like there's a thousand threads labeled "3pt failure" and at least a hundred that are specific to my tractor or its immediate family.

I did take some pics.

The feedback control arm is working properly although it's possible it had something to do with the original problem. I pulled off the relief valve and it's clear and oil is flowing. The supply line from the pump is flowing as well (and the FEL is working properly so the pump is good). So, I'm thinking it's the Position Control Valve, which looks okay but might have failed or have an obstruction.
But there's something I don't understand: where does the Pos Control valve get it's oil? And when the valve is opened to flow oil how does the oil get to the cylinder in order to drive the piston to operate the arms? There are no hoses that I can see nor are there any on the diagrams in the WSM or the parts book. So there must be veins or passages cast into the rock shaft cover that lead from the valve to cylinder. Could something be lodged in one of them? Where are they?
It seems to me it would be more logical that something is caught in the valve but I'm not at all sure. I'll pull the valve today and try and muscle it open. I'll also look for openings that lead to the cylinder.

Thanks Wolfman. Of course the oils pretty much flow through wherever there's an O ring. Duh. I blew out the all the veins and ports in the cover casting (they were clean, no grime, no debris) and opened up the cylinder cover to check in there. There is oil in cylinder (though it isn't full in anyway) and the piston is still sitting, stuck in the top even though the rock arms are slack and the dogbone is completely disengaged. (Yeah, it needs oil to push it down). But I can't easily push the piston down the cylinder. I can tap it with a hammer and force it down. So I took the cylinder out and the piston and I see some scoring on both and even without the O ring the piston only moves reluctantly in the cylinder.
Could THIS be the problem. I am extremely reluctant to pull apart the Position Control valve. Those big flat nuts don't want to move and I really don't want to mess with it. I'm going to try and clean up the scoring and go from there.

Well... I didn't do that, I wire-wheeled the piston and the cylinder and smoothed out most of the scratches so that the piston, dry and without the O ring, smoothly dropped through the cylinder. I put the O ring (and the plastic backer thing) back together and reassembled the whole thing. I figured it might be leaky but would probably work alright.
The O ring makes the piston tight and seems to maintain pressure but it doesn't matter, the rock shafts will rise and fall slowly when the tractor's revved up high but the 3 point hitch won't even lift my puny 160 pounds.
There's nothing left... the only part I haven't pulled apart is the position control valve. I'm debating whether or not to try and find a used part or try and rebuild the one I have. All the parts are available except the housing, but the disassembly looks daunting. When I briefly tried to remove a nut it wouldn't budge.

Wolfman, your opinion about the positive control valve is the chief reason I'm reluctant to mess with it.
The drop adjustment knob seems to function. If I rev the engine and get the rock shafts up (like I said it won't lift anything but will go up and hold my weight in the air once they're in place). If I then drop the control valve down the arms won't move without weight, but will drop if I open the drop speed knob a couple of turns.
This leads me again to the supposition that the pos control valve is bad.
I do appreciates your help. Thanks a great deal.
I'm going to do light stuff with the FEL today and avoid pulling that freaking cover off again (to get the valve out).

See pics, but I haven't touched any of the soft hydraulic lines and I used the FEL and the 3pt hitch extensively before this latest malfunction. Pics aren't great, but I think you can see that the hard line comes up over the transmission from the pump, into a block where two soft lines originate and go up to the FEL valve. (I've never removed those two rubber lines!) The hard line continues to a fitting on the rock shaft cover.
I'll double check that there's no blockage between that splitter block and the rock shaft fitting but I had flow out of the relief valve fitting so... actually I'm going to go through the whole thing again. I'll make sure there's no obstruction all the way through to the pos control valve. And I think there's a port on the cylinder cover. I'll open that and turn the engine and see if there's flow out of that. If there is, it would mean the control valve is functioning and the piston and cylinder are the problem.
I'll also recheck the vent and the relief valve.