Rebuild or replace?

I am focussing in on the Big Hyd. cylinder that lifts my fast hitch/3 point as the problem in not being able to lift much more than a couple hundred pounds. I am wondering/thinking that at high weights that fluid is sliding past the internal seals (it only has a tad of fluid on the cylinder when moving around).

So can I do it or is it better to get another and if rebuilding how do you find a kit to do it?
It is a '56 Farmall 400..

I think you might be grasping at straws by focusing on that cylinder. I'm not going to say that the cylinder might not be the culprit, but I would want to eliminate everything else first.

The cylinder consists of a few o-rings that you can find about anywhere. However, I agree with Rusty in that the cylinder is not likely the problem. It could be something as serious as the pump, or as easy as a plugged filter.

Maybe I just don't understand the system...

I did a pressure check and the pump is putting out 1000psi. The shop manual calls for a minimum of 900psi and maximum of 1500psi.

It does lift but not over a couple hundred pounds, not the 1200 that I need which I believe is well withing it's capability. If the load is too heavy it would lift the front of the tractor but it won't.

I don't understand the pressure relief system. How does it work? How do I test it? I can't wrap my head around what pressure it is relieving and when.. :?

I am trying to avoid changing the fluid until I have figured out what else has to be fixed while I have it out. Getting expensive. It uses a screen for a filter.... as long as it is lifting a little, wouldn't it be able to lift a lot?

I am no expert at all, in fact I don't know much at all when it comes to tractors.
I just rebuilt the cylinder on my SC and my o-ring on the piston was compleatly broken. It was still in the grove but it was very bad shape. Even with that o-ring that bad I could lift the rear of the tractor off the ground with the fast hitch lift.
Your cylinder might need a rebuild, but I am like the other guys, I don't think that is the problem for it not lifting over a couple hunderd pounds.
Ron

Could it be a bad spool valve? Ron

Have you checked hydraulic pressure at the pump?
Did you read that posting on the oldoakfarmalls
on their 460? They had to replace their pump. Hal

I checked the pressure at the rear remote. Both lines checked out. Sometimes a little jerky but would come up with a couple lever movements.. Sometimes it would go to 800 then I would jiggle the lever and it would go to 1000, and sometimes straight to 1000.. I am tempted to switch the control lever things, is that the spool valve?

the pressure relief system is basically a saftey valve in the system. they are set to open when hydraulic ressure exceeds a pre-determined maximum. it is a valve with a spring on it, and when the pressure reaches a certain point, the valve opens venting hydraulic fluid to the return. if it wasnt in the system, when you reach the end of the cylinder stroke, or tried to do something beyond the capability of the system, pump damage, blown hoses, ect can occur. will the cylinder hold a load or does it creep down? if it creeps, that is a good sign of a bad cylinder.

It hasn't creeped down that I have noticed but I will do a measured test to make sure.

So if it is a relief valve that means the relief valve is letting off pressure before it has really built up that much?

I am losing some confidence in my pressure test after reading around and what my shop manual says.
The tester was a 3000psi guage with a quickcoupler on it. It wasn't a homemade thing. I got it from the Deere mechanic in town.It showed the psi but I was that what I need to know regarding the pumps ability to supply pressure? I would think it is but I am new to all this.

I had a similar problem recently. By using a normal 3" x 8" standard 2 way cylinder in place of the IH cylinder, the hitch worked quite normally...good lift power and good speed.

Here is what makes the IH cylinder suspect.... It has a position limit valve in the top end of the cylinder. This little valve has a small (1/8"?) diameter pin sticking out the top end. It was possible to use a clamp like thing to clamp on to the cylinder rod and when the clamp touched the pin (by the rod retracting) then the hydraulic flow was diverted from the high pressure side to the low side. Neat system! But by now the teeny O rings in the valve and pin have totally worn out and that valve is bypassing some oil all the time.

CNH has the seal kit for the cylinder (at least they had it a few years ago when I bought it). I never really got around to rebuilding the cylinder, but as I took in 4 other cylinders to the hydraulic shop, I gave them the IH kit and my IH cylinder to rebuild. They said the internal surface of the tube was badly scored so I told them to go ahead and make a new tube for it. It might have been cheaper to just let the hyd shop supply all the O rings and seals, but I already had the kit and didn't need it for any other cylinder.

What the other responders have said is also a possibility, but I am a firm believer in starting with the simple stuff (and hopefully the cheap solution).

Good Luck

Paul in MN

I was chasing dragons with a plastic sword for a while on my Farmall 504. I installed a loader and did not have near the lifting power the specs stated. Checked my hydraulic PSI at the remotes and it was lower than what the relief is set at. I rebuilt the valves, installed a new pump, and changed the oil and filters. The only thing that happened was I got a faster cycle time on the loader (changed the 12GPM to a 17GPM). It still would not lift the front tires off the ground. Found the pilot relief valve for the remote valves and it was stuck open. Cleaned it up and reinstalled. Still the same issue. Removed it again and found a hardened o-ring that seals it between ports (the o-ring in the manifold body, not the relief). This o-ring had worn a groove in the relief valve, got a new one on the way. I am 100% confident this was my problem. Should have looked there 1st!

Good luck,
Charles