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Discussion Starter · #1 ·
I have a 6400 tractor that seems to have developed an issue with the hydraulics, no power on the loader, will hardly lift anything where before it almost seemed like it was too strong. Yesterday I put a gauge on it and it showed 0 when idling and bottom out the loader att 1200 rpm it showed about 1200 lbs pressure. According to my book should have about 2600 so it seems to be off quite a bit. I did pick up something that probably was too heavy a while ago so my first thought was maybe the relief was stuck open or maybe some issue with the charge pump. Tractor is a 94 with about 4500 hours. I figured there is a lot of these tractors around so maybe somebody might have had the same issues. Anybody have any ideas?

Thanks

Dave
 

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If the problem came on suddenly, pull the drain plug just long enough to check for jewelry, if it plugged filters suddenly it was catastrophic. Most likely not the case, but easy to check and get it off the worried about list. I have a bit of experience with systems 20 years older, nothing as new as yours. That said, if they had a bad charge pump everything was effected, steering, brakes..
 

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Our 6400 has been a hydraulic nightmare since a little over a thousand hours. Have put multiple pumps, valves, Scv outlets and seals all the time so if figure anything out I'll be interested in what it is
 

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Discussion Starter · #6 ·
I guess I'm going to get an operation and test manual and hope that it would have information on the problem, like how to find out if the charge pump is bad or not, don't see any test port on it and don't want to go through all the work of taking it off to find it's not the problem. I'm trying to avoid taking things apart when it's not necessary nothing is a two minute job on this. It has been an ongoing problem and seems to be getting worse.
 

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I bought a digital copy for a tractor of mine and then paid a copy place to print it on some fairly heavy paper. I found not everybody was willing to copy it, because of copyright laws. I had figured that a person has the right to make a copy of what he has legally purchased.
 

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I bought a digital copy for a tractor of mine and then paid a copy place to print it on some fairly heavy paper. I found not everybody was willing to copy it, because of copyright laws. I had figured that a person has the right to make a copy of what he has legally purchased.
I would need to have a paper copy made from digital as well. Would not sell it but for my own use. I could not get a copy made of a family member school picture from probably back in the 1950's because of copyright issues. How in the world would anyone find the company that made school pictures from 60 years ago? :(

Shelia
 

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Discussion Starter · #10 ·
Well now after discovering I can take all the valves off the back of the tractor in one chunk I'm going to get a relief valve and put in and hope that solves the problem. It's only around 120 and by taking the valves off in one piece it will save a lot of work. I've talked to several people that seemed to think it would be a good place to start and having the valves on the back won't interfere much with removing the hydraulic pump and charge pump if the relief valve doesn't do the trick. Yeah I've looked at the book on ebay but thought I'd get a CD but I'm hoping after I change the relief I won't need it. Probably wishful thinking
 

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I would need to have a paper copy made from digital as well. Would not sell it but for my own use. I could not get a copy made of a family member school picture from probably back in the 1950's because of copyright issues. How in the world would anyone find the company that made school pictures from 60 years ago? :(

Shelia
I don't think they copyrighted MY school pictures from a long time ago, but then again I tell my grandkids, Abe Lincoln is in my yearbook (the back ground picture taken in the Library). :lol:

Back a little more on topic, seems that you could print your own, buying heavier paper and having a printer available (if a PDF file). At least that's what I would do and I don't think there would be much of a market to sell them after I got my greasy mitts on those pages. :D But then again, I'm cheap and would only print the pages I needed.

Larry
 

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Discussion Starter · #12 ·
Well after taking the hydraulic pump and charge pump off the tractor replacing all orings and gaskets,I did find one really bad oring where the compensator valve goes on the pump but everything else looked like new and did check the relief valves which were fine put it back together and got 1600 lbs pressure which made me think that my pump was bad. Then I found that the steering system had 2900 lbs pressure, kinda mind boggling that I could get 2900 from the steering and only 1600 on remotes and loader from the same test port. After unending searches to try and find something about someone with the same problem with no luck I went to a different JD dealer in hopes of finding somebody that knew something about the system. The service manager was not to keen on letting me talk to the mechanic but he did. Took ten minutes to tell me the main problem on these tractors is rockershaft valve cracking internally. He said he's changed quite a few, kinda amazing that if it's a common problem I couldn't find anything about it. Anyway went home took it apart and sure enough a couple of nice cracks inside the valve. JD had so much of this they redesigned the valve and according to the mechanic if you have the old style valve you will have this problem. New valve is 2 inches wide verses about 3 1/4 wide on old valve. So now waiting for parts and hopefully will be all set.
 

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Discussion Starter · #14 ·
That's kinda why I didn't rush to the dealer to start with. They usually have the line, bring it in we'll take a look at it, without offering any help. But I guess they're just trying to make some money like everything else. I am buying the parts off of the dealer that helped so they're getting some money.
 

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Well after taking the hydraulic pump and charge pump off the tractor replacing all orings and gaskets,I did find one really bad oring where the compensator valve goes on the pump but everything else looked like new and did check the relief valves which were fine put it back together and got 1600 lbs pressure which made me think that my pump was bad. Then I found that the steering system had 2900 lbs pressure, kinda mind boggling that I could get 2900 from the steering and only 1600 on remotes and loader from the same test port. After unending searches to try and find something about someone with the same problem with no luck I went to a different JD dealer in hopes of finding somebody that knew something about the system. The service manager was not to keen on letting me talk to the mechanic but he did. Took ten minutes to tell me the main problem on these tractors is rockershaft valve cracking internally. He said he's changed quite a few, kinda amazing that if it's a common problem I couldn't find anything about it. Anyway went home took it apart and sure enough a couple of nice cracks inside the valve. JD had so much of this they redesigned the valve and according to the mechanic if you have the old style valve you will have this problem. New valve is 2 inches wide verses about 3 1/4 wide on old valve. So now waiting for parts and hopefully will be all set.
Hi,

I have a similar problem with the hydraulics on a JD 6400. Small difference if the steering seems to have been affected by the drop in pressure also. Can you tell me where to find the Rockershaft Valve that was cracked in your tractor. I am not able to find this valve using Google searches

Regards

Tom
 

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Hi,

When the tractor is revved the steering improves but the back end pressure is still down. The oil filter is new and the pickup gauze / screen has been cleaned with no improvement. For a while the steering would intermittently loose power but recover but now it is permanently not working properly until revved. Pressure at the back end scv valves is measuring 2200psi when it should be 2900psi.

Any ideas what else to check

Regards

Tom
 

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Well your loosing pressure somewhere, not to familiar with this model but if it's a 2 pump system, charge pump provides volume at low pressure and normally when they go bad you can still get pressure at high rpms but will build heat, unless it's completely bad, should be a way to test it's pressure. Have you had and internal problems in the last few years? The reason I ask with Deere if something grinds it's self up internally it contaminates the whole system.
 

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Discussion Starter · #20 ·
On the back of your 6400 there's a valve bank that includes the rocker shaft valve. You have two valves on the left for your remotes then the priority inlet valve and then the rockershaft valve, you should have test ports on that valve, and then two valves for the loader if equipped. My rockershaft valve had an internal crack on the high pressure passageway that dumped pressure back to return. Mine had 1200 lbs at the test port but made 2900 lbs if you bottomed out the steering
 
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