2640 hydraulics

Danfitz55

Member
I have been having some issues with my hydraulics. I changed the fluid and filter and pulled the suction screen. the tractor had been sitting for a long time so the fluid was black and very dirty. I now feel like I have air in the system or possibly the suction screen may be plugged again? Also I noticed that I am leaking fluid coming right out of the shaft going into the pump. is there just a seal there that I can replace. thanks
 

Check to be sure frt pump seal drain line isn't kinked. Frt pump seal can be replaced but pump has to be dissembled. 2640 could have one of 2 different size pumps? Parts photo is larger of the 2 pumps

I doubt air in hyd system is the problem but frt pump destroking valve could have trash in seat area. Does pump have a destroking screw((parts key 6)? If so turn this DS screw in/out with engine running to hopefully dislodge trash. Does tractor have hyd ind pto or hyd hi-lo? If so do these hyd functions operate correctly? Does tractor have a FEL & if so how is it hyd controlled(scv or ind valve)

35564.jpg
 
(quoted from post at 05:05:33 05/01/16)
Check to be sure frt pump seal drain line isn't kinked. Frt pump seal can be replaced but pump has to be dissembled. 2640 could have one of 2 different size pumps? Parts photo is larger of the 2 pumps

I doubt air in hyd system is the problem but frt pump destroking valve could have trash in seat area. Does pump have a destroking screw((parts key 6)? If so turn this DS screw in/out with engine running to hopefully dislodge trash. Does tractor have hyd ind pto or hyd hi-lo? If so do these hyd functions operate correctly? Does tractor have a FEL & if so how is it hyd controlled(scv or ind valve)

35564.jpg

I have noticed that the destroking valve does leak could that have something to do with it. The tractor has an ind pto which works fine and also Hi lo which works fine. The tractor has an SCV. When I first start the tractor the pump chatters pretty bad then it gets better. the more throttle I give it the less of a problem I have turning the wheel and raising the 3 point. just feels like it isn't getting constant pressure.
 
I would check the suction screen again. If it has small flakes of stuff that some are gold colored then your brakes are shot and you will need to fix them ASAP. Another thing that the JD 2640 was bad about doing was breaking the internal steel lines that come up to the Independent PTO and Hi-Lo control on the top of the transmission. You just need to remove the plate that has the gear shifter in it to look at the lines. If one of them is broken you will need to split the tractor at the back half of the bell housing. IF the lines are broken or cracked/leaking it effect the charge pump pressure and that makes the main pump act like it has air in it because it is sucking air because of the leak using up some of the charge pump flow.

I owned a JD 2640 and liked how it handled. I got rid of it because I got tired of working on the hydraulics. It seems like once you have issues on these Mannheim designed tractors they keep happening unless you repair the entire system front to back.

An example is the brakes failing. There is a the suction screen and a filter but it still seems like the material gets into the entire system including the SCV valves. It seems to be worse on the JD 2640 and 2840. A good friend has a JD 2640 that his Dad bought. His brakes failed. We took the entire system apart: main hydraulic pump, steering valve, SCV valves and rock shaft housing( all of these where disassembled and rebuilt). We flushed the transmission case with the top off and flushed every single line/passage. It solved his problems and things have worked great for the 5-6 years since we did that. The trouble is the parts and mainly labor is pretty high to do all of what we did. Even with me not charging him full labor rate it still cost him over $3500 and would have been $5-6K at full rate.
 
(quoted from post at 09:37:41 05/01/16) I would check the suction screen again. If it has small flakes of stuff that some are gold colored then your brakes are shot and you will need to fix them ASAP. Another thing that the JD 2640 was bad about doing was breaking the internal steel lines that come up to the Independent PTO and Hi-Lo control on the top of the transmission.

Checking sump screen again is a good idea but if hyd's operate the same with both the hyd ind pto & hi-lo working well in both positions I doubt the tubes are at fault.
 
So I had recently pulled the sump screen and drained all the fluid. the screen had some debris but not to bad. I also changed the filter. I was hoping that it would solve my problem when I started the tractor it still felt like it had air in the lines. There steering was tough and the 3 point was very choppy coming up. When I drive the tractor and have it moving it works good but when I throttle down the steering gets hard again. I have noticed that when I used the tractor I have to add hydraulic fluid to it I am thinking that its working its way through as its being used but I'm not sure.
 

Disappearing hyd oil can only end up in 2 places either ground/floor or clutch housing if drain hole in clutch housing is plugged. After operation does steering valve feel hotter than other hyd functions? With engine running,3 pt raised look in hyd filler hole behind seat for moving oil.
 
These are a Nasty system to sort out,,try to get a tech manual and look the schematic of the system over to get a better idea of what you have,, sort of like looking at a road map to see where the road goes..I understand them well and hate them even more,, when they are good they are great but when they go bad they are very bad...You are loosing charge oil to the front pump, it could be a worn trans pump, a broken line a worn shaft seal on the hi/Low, or PTO circuit,,or a filter relief valve sticking open. After you do some initial checks you will need to split to at the shifter area and go through each function till you find the oil loss point..You are about to open "Pandora's Box"...One other thing, check to make sure the cone is in the oil filter bowl,, I have seen these get lost out during a filter change and then there is nothing to hold the filter tight, then the filter spins in the bowl till the rubber washer on the filter comes loose sending it through the charge oil circuit, many times when this happens it clogs the passage that can be seen when you remover the brake valve,It would be Lucky for you if this is it....but I have only seen it happen about 5 times in 40 years..."but" it can happen...
 
(quoted from post at 06:44:30 05/30/16)
Disappearing hyd oil can only end up in 2 places either ground/floor or clutch housing if drain hole in clutch housing is plugged. After operation does steering valve feel hotter than other hyd functions? With engine running,3 pt raised look in hyd filler hole behind seat for moving oil.

With the tractor running and the 3 point up I opened the filler hole. What I saw was about every 5 seconds oil would spray out from the top and then it would stop for about 5 seconds. This continued the whole time it was running.
 

That oil your seeing is coming out of the three point control valves. It usually is around the orings that are around the valves. It also could be the thermal relief valve on the rockshaft.

The trouble is the leak your seeing would not take all of the hydraulic flow. Also IF your priority valve is working than the steering should not be hard.

Run the tractor setting still. Feel the steering column before and while it is running. If the steering valves are leaking internally they will cause heat to build up in the column. I will tell right now if your not REAL familiar with setting this steering valve your WILL not get them to work if you tear into them yourself.

All the components of the entire hydraulic system on this tractor have to work for the system to work correctly. You currently know of two issues: The internal leak on the rockshaft control system. Also since that seems to be effecting the steering then the priority valve is not working as it should have shut the SCVs and the three point off so the steering would still be working.

The majority of the hydraulic issues on a JD 2640 will include some combination of the PTO clutch, Hi-LO clutch, the steel lines going to them, the control valve for them, and the charge pump. All of these are in the section right in front of the transmission. I have seen the PTO lines 90% broken and the clutch would still work but the main hydraulic pump would starve for oil. I will second that since your loosing oil, that it is leaking into the clutch housing. That is usually through the Hi-lo clutch pack.

Also hydraulic problems on the JD 2640 and 2840 rarely if ever "work themselves out" They usually work themselves into more MAJOR/expensive problems if run with minor problems.
 
(quoted from post at 19:55:08 05/31/16)
That oil your seeing is coming out of the three point control valves. It usually is around the orings that are around the valves. It also could be the thermal relief valve on the rockshaft.

The trouble is the leak your seeing would not take all of the hydraulic flow. Also IF your priority valve is working than the steering should not be hard.

Run the tractor setting still. Feel the steering column before and while it is running. If the steering valves are leaking internally they will cause heat to build up in the column. I will tell right now if your not REAL familiar with setting this steering valve your WILL not get them to work if you tear into them yourself.

All the components of the entire hydraulic system on this tractor have to work for the system to work correctly. You currently know of two issues: The internal leak on the rockshaft control system. Also since that seems to be effecting the steering then the priority valve is not working as it should have shut the SCVs and the three point off so the steering would still be working.

The majority of the hydraulic issues on a JD 2640 will include some combination of the PTO clutch, Hi-LO clutch, the steel lines going to them, the control valve for them, and the charge pump. All of these are in the section right in front of the transmission. I have seen the PTO lines 90% broken and the clutch would still work but the main hydraulic pump would starve for oil. I will second that since your loosing oil, that it is leaking into the clutch housing. That is usually through the Hi-lo clutch pack.

Also hydraulic problems on the JD 2640 and 2840 rarely if ever "work themselves out" They usually work themselves into more MAJOR/expensive problems if run with minor problems.

So I just had some time to check on the tractor. After I let it run for awhile the steering column did build up some heat but it was not hot. I also tried to work the steering wheel back and worth again and it was tough then I engaged the PTO and it got even harder. I also worked the 3 point it was a little choppy and then when I engaged the PTO it stopped completely and when I disengaged it then it continued to go up. I think I am going to check the lines in the clutch housing. Will I be able to inspect them if I take the cover off where the shifter levers are?
 
(quoted from post at 16:05:02 06/04/16)
(quoted from post at 18:22:06 06/04/16)

Will I be able to inspect them if I take the cover off where the shifter levers are?

After removing shift cover you can blow air into tubes and listen for escaping air.

Ok I took the cover off and I'm not sure what I'm looking at . Are the tubes in the photo the ones you are referring too?
36724.jpg
 
Yes but you really can't see much with out splitting in that area, and even then you need to look very close at the pipes for hair line cracks...
 

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