John Deere 4430 3pt Hitch Issue

I have a John Deere 4430 which I have used on my farm for the past 2 years. It is a fantastic tractor. Quad with FWA. It is our work horse tractor. No complaints except the hitch. Ever since we bought it the 3pt hitch has always been iffy. Sometimes it would settle while working out in the field. Bent a PTO driveline one day because of it. It also would not go up all the way. We used it to ditch last spring and noticed that if the hitch was completely lowered with a load on it (as it is with a ditcher or plow), it would not come back up. However, if it was completely lowered without a load on it, or if it was lowered with a load but not completely (as with a box scraper that won't let it go completely down) it would come up immediately. We didn't worry about it too much, because we would just slowly run the ditcher into a gate enough to get it to lift up a little. As soon as the implement lifted by an external force, it would then cause the hitch to come up as commanded. Pulled it in to the shop for winter service and to fix the hitch. Found that there were several problems which I surely thought would fix it. The spring loaded nut was loose, the steel strap that holds the 3pt control linkage to the valve was loose and was allowing it to move. I adjusted the linkage strap and torqued the spring-loaded nut. Went through the service manual and performed all hitch adjustments. Thought this had solved it because the hitch was very responsive and would go up all the way. However, I hooked a 4 bottom roll plow onto it and drove out to the loading dock where I could let the plow hang and bottom the hitch out. It bottomed out out and I immediately pulled the lever back to raise it and it raised. Thought it was solved, but realized that the longer I let the plow hang without commanding it up, the longer it would take to signal the hitch to raise. After a certain point it would not raise at all and I had to ram the plow into the loading dock to get the hitch to come back up. When the hitch won't come up, the control lever seems easy to move, as if the linkage in the valve is being interfered with. I am stumped. Wanting to pick the brains of some people that know more than I do about these great tractors.

Welcome to the best tractor discussion forum on the planet! You performed 2 good things which were tightening the big nut on the control mechanism shaft & adjusting the L/D control per service manual. I think plow hanging on 3 pt fully lowered is bending L/D control shaft in the opposite intended direction adversely affecting 3 pt linkage. Have you checked stand-by pressure? I'd set stand-by pressure at 2350 psi.

(quoted from post at 16:25:09 11/23/14) Welcome to the best tractor discussion forum on the planet! You performed 2 good things which were tightening the big nut on the control mechanism shaft & adjusting the L/D control per service manual. I think plow hanging on 3 pt fully lowered is bending L/D control shaft in the opposite intended direction adversely affecting 3 pt linkage. Have you checked stand-by pressure? I'd set stand-by pressure at 2350 psi.

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Hey thanks for the response!
I will check standby to assure its at 2350
When you say LD control shaft, which shaft would that be?

(reply to post at 19:54:53 11/23/14)

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L/D shaft is parts key 8. The 3 pt drawbar support is attached to trans case by means of the L/D shaft. Load applied to 3 pt bends(arches) the shaft therefore changing the 3 pt control valve settings to raise/lower 3 pt according to amt of bend in the shaft.