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Discussion Starter #1
guys on my jd400 backhoe / jd 2020 tractor i have developed a hyd. leak on the right side above the pick up screen , it a 3 bolt cast piece,

maybe a return,, that bolts to the side of the trans/rear does this take a gasket or just silicone ??
 

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Pressure Control Valve.

Two o-rings.


TP5068_________UN01JAN94.gif
 

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That is the pressure control valve for the JD400. It is a little different than the 2020 because of the backhoe connection. I am a little confused about the hole in the center of the larger oring being brazed shut? It also appears that the braze is cracking part of the way around. Don't think the crack is causing your leak though. Your screen look awful. Maybe some water at some point causing oil to congeal? Was oil clean looking?
 

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jd110
I think I've never seen before the large hole plugged on pressure control valve similar to photo. My guess is a ""shade tree mechanic"" plugged it searching to fix the closed center hyd system that they knew very little of how it was designed to function.
Jim
 

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Discussion Starter #6
should i drill a hole in the brass? is this one junk? where could i get a used/new one?

would some diesel (maybe a gallon) in the bottom of the trans help get rid of the sludge crap??
 

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My take on this:

The passage that is brazed is the "return to sump" port. The valve (#25) regulated the amount of oil supply/pressure needed to operate steering & brakes. This is a safety(Priority) feature. I'm thinking the valve(#25) itself is removed, or stuck open. Someone filled the passage to eliminate to oil flow into the reservoir.
Disassemble and check for a missing, or stuck valve.
pressure control valve diag.jpg

mvphoto5492 (2).jpg

Now, to answer your questions:



should i drill a hole in the brass?
It is possible to drill the brass out.


is this one junk? where could i get a used/new one?
Possibly.
New valve housings are quit expensive. Used/salvaged/ rebuilt valves may be found. Do an internet search.

would some diesel (maybe a gallon) in the bottom of the trans help get rid of the sludge crap??
Maybe. I doubt you will get it all out. Remove the drain plug on the bottom of the transmission case. Flush out what you can. Clean the sump screen and install a new hyd. filter. Run the tractor a day, or so. Check the sump screen for more sludge; and replace the hyd. filter again.
 

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Discussion Starter #8 (Edited)
wowzers a new pcv costs about 1100-1200.00 looks like someone has ground the back of mine and the valve and it is not true, may look into salvage part, any salvage places you guys recommend ?? ,, ill take some pics of the side of the trans and make sure the oil holes line up

oh i took the valve apart and everything moves free did look like it was missing #2 #4 and #6

the steering seems to work fine
 

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If it were mine, I'd first try drilling the brass weld out.

As for the mounting surface, place the housing in a vise and run a large flat file over it. Use a new file. Take your time with it.
Once the mounting surface is fairly smooth, install new o-rings and apply Permatex Loctite 518 on the entire mounting surface. Bolt it in place and wait overnight to operate the tractor.

If this doesn't work, you can start shopping for a salvaged PCV.
 

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Discussion Starter #10
here is the mating surface on the side of the trans the brazed area of the pcv mates to the area with the yellow bolt head exposed (maybe a flow adjuster or maybe not supposed to be there) 20170417_132903.jpg
 

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Discussion Starter #13 (Edited)
removed it ,, any idea what the housing part number would be ?not finding much for pics to make sure im looking at the right one,,, i think ill try to order a new one, the plug has a nut brazed to it 20170418_172202.jpg
 

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I am glad you got that sump screen out. It way worse than mine was. You can try and flush out some of the sludge. Leave the trans filter and sump screen off and come in thru the rear inspection plate with desiel fuel in a hand sprayer and get what you con. I had to do mine twice but it cleaned up. Good luck. I found the notes from when I did mine. The mixture I ran in mine was 3 gallons desiel with 10 quarts ATF fluid. Let it run and work the three point then flush it, fill it with hydraulic fluid drive it around some then reflush it. Change tranny filter every time and I put in a new sump screen. Good luck and change those shifter boots.
 

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Shane, was this threaded into the transmission case, or just slid inside??




If it was threaded, it's possible the set-up below was original to a replacement transmission case. Of course, some 400 series, without a backhoe, used this set-up.

TP26537________UN01JAN94.gif
The previous owner may have installed that plug, to replace item #21 (R66084 Fitting).

There were quite a few variation on these Industrial Tractors.
What is the serial number and model of your tractor? Is there a tag on the tractor?



Edit:
T30968_________UN01JAN94.gif
 

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If it was threaded, it's possible the set-up below was original to a replacement transmission case.
This is just speculation:
What I'm trying to say is, if the transmission case was replace for some reason, parts acquired from a Agricultural tractor.
If so, they would have tried this method of installing a plug in the case. :dunno:
 

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Discussion Starter #17 (Edited)
yes the above brazed plug was threaded into the side of the trans,, the trans is threaded too, everything seems yellow and doesnt look like it has other parts added serial number of tag on the side of the trans attached

Thank You so much for your help guys, im new to tractors and just want to do what is right with this thing ill get some more pics of the trans 20170414_113635.jpg 20170414_113628.jpg
 

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If the trans case was replaced with NEW case, it would not have been green.

If it were mine, I'd first try drilling the brass weld out.

As for the mounting surface, place the housing in a vise and run a large flat file over it. Use a new file. Take your time with it.
Once the mounting surface is fairly smooth, install new o-rings and apply Permatex Loctite 518 on the entire mounting surface. Bolt it in place and wait overnight to operate the tractor.
After doing the above, leave the plug out. re-assemble the PCV and test the operation.
 

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Discussion Starter #19
ok ill give it a try ,, could i use jb weld on the back of the pcv to true it up ,, somebody used a grinder on the back and took out to much material
 

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It's worth a try.. :unknown:
 
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