My 3pt has drifted down for a couple years. This past Summer when brush cutting and heating up the oil it got worse. Would "relift" every 2 seconds or less. So this Winter I decided to tear it apart.
I lifted it off by hand. I don' recommend that method. It's heavy and awkward. I removed the lift arms to make it as light as possible.
When unbolting it only remove the ring of bolts around the outer edge. There are four bolts that hold the lift cylinder housing and valves to the top cover. Don't remove those. You must remove the cover with that assembly still bolted to it. That part sucks.
The cover will only come upward about 3/4" before the pressure relief valve sticking forward from the lift cylinder housing hits the top of the trans case. So you lift it level upward until it hits, then raise the rear of the top cover upward until you can slide it backward to allow the pressure relief valve to clear the case. Really sucks doing this by hand. Either have a helper or a cherry picker.
Once you get the top cover removed you are looking into the open case between the rear end and the transmission. The Independent PTO clutch is in there. Also the hydraulic speed valve.
I didn't plan to change the hydraulic fluid so I was especially careful about dropping anything in there. Scraped off the old gasket. Replaced the pickup tube and O-rings. Replaced the large O-ring next to it. Replaced the top cover gasket and stuck it down with Hi-Tack. Didn't want to worry about the gasket when reassembling.
I removed the lift cylinder housing with valves from the top cover. I might have been able to get the piston out without doing that but wanted to hone the cylinder so removal was necessary.
To remove the cylinder housing you must unhook the lift control linkage somehow. I chose the minimal route. The linkage is very complex. I believe if you just start taking it all apart you will find yourself in a mess when you try to reassemble. So I unbolted the linkage from the cylinder housing and gently laid it back out of the way. Then removed the cylinder housing by taking out the four bolts that hold it to the cover.
To remove the piston from the cylinder I used air. Doesn't take much so be gentle. The first pic shows which port to charge with air. Piston comes right out.
The cylinder was scored pretty badly so I honed it to remove any sharp edges. Didn't try to get rid of all the scrapes. Would need to be bored for that.
I also used Emery Cloth on the piston to remove any sharp edges on it.
The piston has an O-ring and a plastic flat ring that share one groove. O-ring is toward the top of the piston. flat ring toward the bottom.
I liberally used some Mystik grease I had on hand. Even then I had to use a Dead Blow hammer to get the piston back into the cylinder with the new rings installed.
Now I ran into my first snag...... The top distribution unit bolts to the cover. It barely clears one of the bolts that holds the cylinder housing to the top cover. The clearance is soooooo close that if the head of the bolt isn't turned to exactly the right spot you can't get the bolt to fit.
Looking at the first picture. I used a black tipped phillips screwdriver to point at the bolt in question. The flat side of that bolt head must be parallel with the edge of the distribution unit or it causes it to shift to far for the bolts to enter. That little trick cost me about 30 minutes trying to figure out why I couldn't get the bolts to line up......
Okay, ready to bolt the unit back on the tractor. Cherry Picker this time!!!!
Really easy to install with the picker. I installed the pickup tube into the tractor housing. Lubed the end of it real well so it would easily slip into the top cover.
Oh, one tip. Before I removed the lift arms from the splined shaft I marked the placement with a chisel. Made reinstallation a lot easier. Put a mark on the shaft and a corresponding mark on the arm.
When I get the other current repairs done I'll report the results. Gotta be better than it was.
When installing, you have to let the front down first so the pressure relief valve can get under the case. Then gently let the rear down until it's sitting above the tractor level, with about 3/4" gap. Then move it around until the tube locates itself in the top cover hole and then let it down.
