ford 600 lift arms bouncing

just got tractor back together and lift arms work but now they bounce up and down. the bounce stops when lifting but starts as soon as I take my hand off control. does this mean linkage is in need of adjustment? thanks

Do they drop a bit from the desired height, then jump back up to the desired height and then drp a bi again and repeat, over and over? If so, that is called hiccuping, and it is caused by an internal leak, usually in the lift cylinder itself, and the linkage adjustment is probably fine. When in position control mode, the control handle and it's linkage tell the system where you want the arms to lift to, and once they get there it closes the control valve and stops lifting any higher. Then the fluid in the cylinder that should be holding up the load leaks past the seals and the arms drop a little, and the linkage senses the drop and compensates by opening the valve and letting more fluid pump into the cylinder and it lifts back up to the desired height and then the linkage closes the valve, assuming that the arms will maintain that height and then more fluid leaks past the seals and it repeats, over and over.

You'll need to pull the lift cover and replace the seals in the lift cylinder. You should go through everything while you have the top off because taking it off is the hard part and you don't want to have to take it off again 6 months down the road because something else is wrong. Buy a hydraulic top cover repair kit, which contains all of the various o-rings and seals that you should replace under there, and replace them all, and then you should go through the adjustment procedures just because you already have it opened up and you want to make absolutely sure everything is correct before you close it back up.

I'm with Sean on the this. You have a small leak on the piston side of the hydraulic circuit. The trick is to find out where the leak is.

You can often see the leak if you pull the PTO round port on the left side of the center housing. Start the tractor, life a heavy object with lift. Turn the tractor off. Then take a look around inside. You can see the cylinder assembly, but it will take a mirror and flashlight. Look for a small drip. Most likely it is the piston O-ring or the control valve. Sometimes you can see some of this by pulling the fill plug and looking inside with that flashlight.

Other possibilities are one of the O-rings between the cylinder assembly and the top cover. But they rarely give any problems.

Here is a picture of a leaking control valve.

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