Go BottomJohn Deere 2640 hydraulic issue
 | hydro420
Join Date: May 2010 Posts: 5 
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2010-06-01 171256
Hello,
my uncle has a 1976 John Deere 2640 tractor. We seem to be having an issue with no hydraulic pressure in the hoses around the pressure valve. He is smart enough to just check the filters and oil and what not. There is some internal problem in the valve or somewhere near it is our conclusion.
I'm not as fluent with this stuff as my uncle but any suggestions would be helpful. I could try to elaborate on the issue given some direction.
Thanks,
hydro
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| hardwood
Join Date: Dec 2002 Posts: 3583 iowa 
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2010-06-01 171261
When you say no pressure in hoses around pressure valve, do you mean the valve that operates a remote hydraulic cylinder?
Does the power steering and brakes work?
Maybe we can get a better fix on your problem from there, one step at a time. ....
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| hydro420
Join Date: May 2010 Posts: 5
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2010-06-01 171263
I'm pretty sure the power steering and brakes work.
The problem with the pressure is on the back of the tractor where there are four hoses, 2 in a box on each side, for equipment, such as a hay bine. It won't lift the hay bine up.
The valve I'm trying to describe is located under the right side step when you are sitting on it. It was stuck closed. We haven't put it back together since we took the valve off.
Do you think that valve is the problem or does it sound like another problem. I hope I made more sense. Thanks for your help man. ....
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| hardwood
Join Date: Dec 2002 Posts: 3583 iowa
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2010-06-01 171268
If my memory is correct all the "40" series farm tractors use a single front mounted pump for all functions. So if the power steering and brakes still work fine then I'm betting you have the problem in hand with the valve its self.
To a person not used to dealing with hydraulic valves they can be a bit overwhelming when you take one apart and all the little springs, balls, etc. start falling out. I'm sure that Deere has an overhaul kit for the valve, but perhaps having a Deere service person or someone in a tractor repair shop do the overhaul may prove to be a lot less frustrating. ....
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| hydro420
Join Date: May 2010 Posts: 5
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2010-06-01 171276
It may be the valve. Do you think that the valve being stuck shut suggests that the valve is bad or could this suggest another problem? Or do you know if there are any potential problem zones between the pump and the back of the tractor where the equipment hook ups are? Maybe a place where a leak could occur or any other valves?
I sure do appreciate your help. We like to try to fix it ourselves before we take it to the shop. Its an inconvenience to take it to a shop. We live pretty far from a shop. ....
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| hardwood
Join Date: Dec 2002 Posts: 3583 iowa
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2010-06-01 171279
OK; Maybe we can confirm a couple things for now.
When you say the valve is stuck shut, I'm taking that to mean you cannot move the control lever that operates the valve, correct?
Also I'm understanding that you have removed the valve body and have disassembled it, correct?
Did the three point hitch operate normally before you removed the valve? If yes then the valve you have removed is likely your culprit.
I'm not going to tell you that you cannot overhaul and re assemble the valve yourself, but lots of little things have to go in the correct places and in the correct order.
A JD overhaul kit likely has the instructions on how to do the job.
Nothing will be lost by cleaning things up really good and re assembeling it without a kit, perhaps a bit of dirt or something has caused it to bind up.
Best of luck, as "Murf" would say.
Frank. ....
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| hydro420
Join Date: May 2010 Posts: 5
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2010-06-01 171285
When we say the valve is stuck shut, we are not talking about a valve with a lever as far as we know. When sitting on the tractor, on the right side under the running board where your feet go, this is the location of the valve we took off. Its bolted with three 3/8" bolts to what we think is the side of the transmission. That's the valve we took off.
When you said lever, were you meaning the lever that is connected to the rectangle box on the right side on top of the rear axle? The one that controls the flow of the oil to lift and lower the equipment. This lever works fine, but there is no pressure to lift. We've put new valves in it in the past.
We did remove the valve, but we did not take it apart. And the three point hitch did work before hand. Although when you shut off the engine, the arms would come down fast. We didn't use it after this because we were afraid it might cut a groove if the o-ring was bad. We have only been using the drawbar and the hydraulic hoses.
This all worked in the fall when it was placed in the barn and in the spring when the equipment was hooked up the levers worked but no equipment was lifted.
Thanks,
Nathan ....
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| hardwood
Join Date: Dec 2002 Posts: 3583 iowa
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2010-06-01 171291
Nathan;
OK, we are talking about two different things here. My assumption was you were working on the valve you describe as being on the rear axle that controls remote cylinders.
Now the "Valve" you decribe as being fastened on the side of the transmission. I can't tell you what it is, it may be a flow diverter, something to do with the brakes, etc. I don't know.
As to the three point dropping after engine shutdown I think that's just a John Deere thing, some do it some dont.
Frank. ....
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| hardwood
Join Date: Dec 2002 Posts: 3583 iowa
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2010-06-01 171293
An added comment on the three point droping after engine shutdown. The real John Deere farm tractors I had when we farmed, none of them would hold the three point up for more than a few minutes. My little wannabe John Deere 4310 compact will hold the three point up for weeks without droping even with a heavy implement attached. ....
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| jdgreen
Join Date: Jul 2003 Posts: 232 Maryland
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2010-06-01 171301
Nathan, the valve you are referring to under the step is the "pressure control valve". I prefer to cvall it the priority valve, since it gives priority oil to the steering. If the pressure falls below around 1750 psi, it will shut off oil to three point hitch and hydraulic outlets.(scv's) It can definitely be a problem, but I am more concerned about the three point hitch that you say falls down fast with engine off. You could be losing so much oil in the hitch that there is nothing left for the outlets. Do you have any way to test your hydraulic pressure? The stroke control valve in the pump could also be worn and not allowing the pump to build enough pressure for rear outlets. There is an adjusting screw on the bottom of the pump to adjust pressure, but if there are large internal leaks such as you have in the three point hitch, you may not be able to adjust enough to overcome the leak. Have you tried to lower the hitch and see if it improves hydraulics? Sometimes it will depending where the leak is in the hitch. ....
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