1850 3 pt hitch

The lift arms on my 1850 settle down as soon as you shut it off. The 3 pt works as it should when running, so the seals on the piston are good and the elbow isn't broke off. The arms stay where you set the lever when it's running, just settles down when shut off. I have to take the hydraulic off to replace a broken bolt under the rockshaft and while I'm in there I would like to fix whatever inside holds the arms up when it is shut off. Anyone know what it's called or a part number?? I've been around Oliver's since 1973 and know that the arms are supposed to stay up when tractor is not running. I have 2 1550's, one the arms stay up and the other doesn't. It will be next after the 1850 to get fixed if I can find out what the part is called. The first 1850 that I bought in 1973 the arms would settle down when I looked at it. My brother told me they were supposed to stay up, so I got the dealer to fix it before I bought it and they stayed up as supposed to for as long as I had the tractor. Thanks, Chris

That relief elbow might not be broken off, but did you check for cracks?

Dont have it off yet, gotta finish the pto first.

While you have the Hydraulic Unit off. I would replace the Street Elbow fitting, but I bet at this point it has been done by now. I would also check the pressure relief valve that is threaded into that elbow. I have had to adjust everyone I have ever had a part. The next thing would be to reseal the piston on the internal lift cylinder. The last thing I would go thru is the servo valve, take it apart clean and check. That valve has just orings and copper washers to replace unless there is broken internal parts, which is possible. The servo valve is what actually controls the three point action and the hold postion that you are talking about. I bet your problem is in the servo valve.

If the elbow was broken off or cracked, wouldn't that let the arms down farther than where you set them while operating and it would be constantly raising the arms to where they were set originally? Would the lift arms even raise with the elbow broken? This doesn't do that, when running, you set the arms where you want them and they stay there. Confused

I'm not sure I'd agree that working as it should when running means your piston seals are good. While I've never had it specifically on an Oliver/White, I've had a few tractors where the arms drifted down when the tractor's shut off, but operate and hold the load fine while running. It's always been the piston seals.

The pump is more than able to keep up if the seals are bypassing a little: probably only bypassing/leaking past the seals at 0.5 - 1 GPM at most, while the pump is 15 GPM, so it's more than able to keep up and maintain position. Because the other side (where it's leaking to) is open to tank and you're not appreciably changing surface the area of piston, it's still got all the force/power it needs to lift heavy loads. And because the position/servo valve is a constant feedback, it will still maintain the position you set it at while it's running. It just means your pump is always working a little to keep up with the small (but constant) bypass.

I'm not saying that's necessarily your problem. It could be bypass/leaking somewhere else in the system (valve spool would be my next guess). But the lift cylinder/piston seals would be my first suspect.

This post was edited by DanielW on 07/28/2023 at 10:55 am.

What I said in my last post would also apply if that relief elbow was cracked - it will still maintain its position and work with the tractor running because the pump can keep up, and because the position setting is a constant feedback. The only time it would wander down while running is if something were leaking so badly that the pump couldn't keep up - which would have to be one holy heck of a leak/crack.