960 hitch pulsates while trying to lift

nwford

Member
I'm working on a 960 I bought at an auction years ago. When I attempt to raise the three point the arms shake or pulsate on the way up with no weight on them. Does the same with 500lb of suitcase weights but it will lift them. I've swapped the hydraulic piston pump with on off of a working tractor, replaced the orings on both ends of the hydraulic suction and pressure manifold from the pump to the transmission. I've also changed the hyd oil. Still pulsates. I see no oil swirling in the bottom of the case like the relief valve is opening and no oil seeping from the rockshaft valving either. The cam follower pin is about half worn from what I can see. I'm wondering if there is an issue with the valving in the rockshaft. Any ideas?
 
Your symptoms are usually caused by non functional valve(s) in the pump.

This can be caused by dirt/debris in the valve champers, broken valve springs, etc.

A common cause is silicon goop in the valve chambers resulting from someone using such goop in place of the proper gasket somewhere.

Though the cam follower pin should be replaced, it is not causing your symptoms.

Dean
 
Dean is probably right but do you have all the air out of the system?. Loosen the 3/8 pipe plug on top front of the pump and check for air.
 
I have bled both pumps by removing the plug on the head section of the hyd pump, installing a hose barb fitting, a hose and routing it to the fill port on the rockshaft. I've started the tractor and let it run for a couple minutes on both pumps. Reinstalled the plug and still same pulsation in the lift. I've disassembled the original pump and don't see any damage to the ball seats. The gasket in the pump head didn't appear blown out either.
 
What you did with the hose is good but it may take more than a few minutes. Took about 20 for my 2000. Used a clear hose and it looked like solid fluid but when I shut it off it was filled with 1/2 inch bubbles. I had the same chattering in cool weather but OK in warm. New balls and seats in the pump did the job.
 
It could be a leaking valve somewhere in the system. My lift system keeps correcting after I rebuilt it. I found out that after I put a hay fluffer on it and left it up after shutting the engine down I can hear this tapping sound right under the seat. I'm sure it's the pressure relief valve under the 4 bolt cover that's leaking. It could be one of the other valves in there but that's the easiest one to start with.
 
If a leak, that would be one pulsation rate that I think would differ from a pump caused pulsation. Leak rate determined rate vs a rate related to engine speed.
 
I replaced the valves in the pump. Pump seals and bearing. New gaskets. Reinstalled the original pump that I rebuilt back onto the tractor. Bled the system. Started the tractor back up and it's doing the same thing. hitch pulsates or shakes slower with weight on it.
 
(quoted from post at 23:42:06 05/27/20) I replaced the valves in the pump. Pump seals and bearing. New gaskets. Reinstalled the original pump that I rebuilt back onto the tractor. Bled the system. Started the tractor back up and it's doing the same thing. hitch pulsates or shakes slower with weight on it.
oing the same thing over & over & expecting different results is the definition of insanity. .....So, I see you didn't say jack about the rate of pulsation!?
 

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