3-Point Hitch John Deere 4400 Rock shaft Control Valve Repaired (3-point would not lift weight)

   / John Deere 4400 Rock shaft Control Valve Repaired (3-point would not lift weight) #1  

aschubert

New member
Joined
Apr 29, 2019
Messages
1
Location
NW Lower Michigan
Tractor
John Deere 4400
I recently spent considerable time spelunking through these forums trying to find out how to fix the problem with my JD 3-point hitch not lifting any weight. Or only lifting slowly at full rpm. While my only tractor is a JD 4400 perhaps this will apply to others as well. I was not satisfied with the end solution in the troubleshooting guide being to replace the rock shaft control valve at $500 or more.

Bottom line: The valve can be disassembled and fixed if has not been damaged by something harder than the steel. And no springs are broken or seals destroyed.

The first time the hitch would not lift weight was about a year ago. I read here and learned after disassembly that the in-line filter screen (inside of part AM123226) is prone to breaking loose and going downstream into the valve. And so it did.

In the first picture I have named what I THINK are the valve ports based on studying the hydraulic diagram for the internals of it. I will refer to them that way here. If the names are incorrect someone can correct me.

Photo 1 - Rockshaft control valve layout.jpg

In any case, once the cover was removed it was easy to see a bit of screen sticking out of the dump valve port (see second photo). That valve is spring-loaded from the inside. All I had to do was to hang onto the bit of screen with the needle-nose pliers and then press the valve pin inward with a dowel to dislodge it. I then replaced the inlet part, AM123226, with a new one with a screen in it.

Photo 2 - Filter screen found in dump valve.jpg

I was quite pleased with myself, thinking the problem solved until the same symptoms reappeared this winter. I once again pulled off the rock shaft control valve. No bits of screen were visible sticking out. After pulling almost all of the valve apart and reassembling the problem persisted. In some desperation I decided to fire up the tractor with the rock shaft cylinder cover off. When I actuated the 3-point lift lever I got a feeble spray through the port that feeds into the rock shaft cylinder. After verifying the port was clear between the valve and the cylinder I started the tractor with the rock shaft valve cover off and again operated the lift lever.

I am now intimately acquainted with hydraulic fluid as is a good part of my garage. But I did discover that fluid was being pumped out the port on the side of the valve, the relief valve (I think) when it should not have been.

I had missed this valve on the first clean out. It is located under a plug that is overlapped by the large valve cap where a hex wrench goes. I thought it was a press fit but it can be removed with a little prying. First remove the large valve cap with the hex wrench fitting first. And there's the little gremlin (3rd photo). Again, this is a spring loaded valve so you just need to release the screen by depressing it inward a little.

Photo 3 - Filter screen found under relief valve cap.jpg

Well, my first and probably over-long post. I leave it here as a trail of pebbles for someone else who might have the same or similar problem.

Good Luck.

Art
 
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   / John Deere 4400 Rock shaft Control Valve Repaired (3-point would not lift weight) #2  
:welcome: to TBN

Your first post was a powerful one, to say the least. Great instructions and pics to go with.

I read about the screen getting blown out and mixed in the control valve early on thanks to TBN. I changed out that screen with the fix recommended.

But your primer on searching and finding the problem certainly provides good help for others.

You are an asset to the forum with just a single post. :thumbsup:
 
   / John Deere 4400 Rock shaft Control Valve Repaired (3-point would not lift weight) #3  
Great post! Thanks!
 
   / John Deere 4400 Rock shaft Control Valve Repaired (3-point would not lift weight) #4  
Much appreciation for posting this. My 4400 had the same issue where it sucked the screen in. Doesn't look too difficult getting in there and getting the screen out without having to purchase a whole new control valve.
 
   / John Deere 4400 Rock shaft Control Valve Repaired (3-point would not lift weight) #5  
Welcome! Come back soon! But hopefully not with problems.

I didn't have problems with screen in my 4310's but the shaft and all the actuarial stuff that should make it work was all rusted and needed taken apart, cleaned and lubed. I did pull the valve apart too as you did. The tube with the screen filter in it would NOT unthread. The aluminum housing had corroded. I had to almost curse and buy a new one.
 
   / John Deere 4400 Rock shaft Control Valve Repaired (3-point would not lift weight) #6  
I had the same problem. One day the lift arms on my 4400 were working, the next day the lift arms were completely dead, hanging limp no mater the lever position. Read your post, removed the rock shaft valve cover and saw some screen in the dump port. I took hold of the screen and tried to push the port piston in but it was stuck and the screen ripped. When the plug finally moved the remaining screen disappeared inside, but now the piston moved freely. I removed the rock shaft valve and then could see screen in the main valve through what I assume is the main hydraulic oil supply port. I worked the valve back and forth and with a hooked pick tool extracted a big chunk of wadded up screen. Looking inside I could see another piece of screen through the hole in the main valve piston. Same technique extracted a smaller wad of screen. I did not disassemble the main valve - maybe that was a mistake. There was no screen in the relief port. I removed the large plug that partially covers the relief port, pulled the piston out and found nothing inside. I didn't pay attention to the orientation of the hole through the piston so I am hoping the orientation doesn't matter. All is assembled and reinstalled. Awaiting the new filter screen part to give it a try. Thanks so much to everyone for taking the time to share your experience, especially to you aschubert. I live a long way from a JD dealer. You saved me a lot of time and money and down time.
 
   / John Deere 4400 Rock shaft Control Valve Repaired (3-point would not lift weight) #7  
I recall early on when my 4300 was new, that there was a problem with an inline screen that could grenade and get pushed into the valve. There was a retrofit that I added to my 4300, and will have to search back to see just what it was. My 4300 is a '98.
I'll look for it. (edit.. found it right here, thanks to "aschubert". )

Found some info. Link to a TBN discussion about that filter/screen.

The replacement screen is LVA12302. Is longer, and needs to have some replumbing to fit. Think it is more robust and can't blow out like the early ones did.
New lines to fit may be LVA11765 (left side) and LVA11210 (right side) with T77932 o-rings. (according to my notes from way back)

rrbrem
Welcome to TBN
 
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   / John Deere 4400 Rock shaft Control Valve Repaired (3-point would not lift weight) #8  
Fantastic thread. Thanks to aschubert for posting his results. Normally a first-timer comes along needing help. In this case, aschubert comes along with a very helpful description showing the issue and resolution in one grand-slam.

I have a good friend with a 755 that has a pulsating 3 PT. We closed off the valve that slows the drop and it's much less of an issue, but it still will dip a little and then immediately comes back up to position. Not sure where to go with that.

edit: anybody know what could be causing this pulsating?
 
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   / John Deere 4400 Rock shaft Control Valve Repaired (3-point would not lift weight) #9  
Thank you for this information! 3pt hitch wasn’t working at all on my new(to me) 4200 & found a small piece of metal in the rock shaft valve. Removed metal & reassembled & 3pt hitch works perfect.

IMG_0355.jpeg
 
   / John Deere 4400 Rock shaft Control Valve Repaired (3-point would not lift weight) #10  
My 2005 - 4310's rockshaft quite working 6 years (2017)ago, I began troubleshooting and here is what I found
1. The power beyond filter (bronze filter) was installed backwards by the tractor dealer (no out of business)
2. The bronze filter was in pieces, tore down the tractor, looking for debris at the screen (intake to the rockshaft control valve.
3. Found another piece of brass where the screen was suppose to be, but never found a screen.
4. Put is all back together and it worked,,,, until last week (June 2023)

I searched the entire internet for help, since there is not a dealer near me any longer. I bought the 875 page technical manual so I had a good idea of how the hydraulics worked (well worth $25).

Found this link online, it was extremely helpful in giving me the confidence that I could possible resolve the issue myself.

I tore the machine down, leaving the the rockshaft on the tractor and accessing by removing the left fender. I found this in the entrance to the rockshaft control valve. Here is where the screen ended up, along with a lot of bronze. I removed this debris and the control valve. I found one more piece of screen in one of the valves. Put it back together and it worked, sort of. Under idle, no movement, at 2000 rpm would move arms but not with a load. Knowing that my front end loader was working fine, I knew I had pressure but no volume to the rockshaft cylinder, something was bypassing.

Talked with nearest dealer, $750 for a near control valve. Decided to take valve apart again, and removed all the spool valves. Laying the pieces out on a clean cloth and taking pics along the way. I got down to the last valve spool and could not figure how to remove the cap. I finally figured the cap had a hole in center with threads, found a small screw that fit and could grab the screw and pull the cap clear (had an O ring on the cap, very tight). Here is what the problem was. I removed this bit of bronze, cleared the the relief valve. Now all parts were removed from valve body. I cleaned everything and put the valve back together. Put the valve back on the tractor, and it works like new.

Many thanks a Aschubert for this post
 

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