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Discussion Starter · #1 ·
Our STX threw a transmission fault due to low oil pressure. The tractor will move about a foot when put in gear before it kicks into neutral. The tranmission oil pressure is around 160psi at idle and 190-200 at full throttle. I am told it should be 250-300psi. We cleaned the main pressure control solenoid spool in the front of the tranmission. It had pressure for about 15 minutes but when we shut it off and started it again the pressures was back to 160psi at a idle. The spool had some wear in it. The tractor has a powershift transmission and has around 2000 hours. I changes the oil filter and it was perfectly clean. Does anyone know how to correct this problem? A new reman main pressure valve block is around $4500. Any Help would be greatly appreciated. Thanks SouthernSK
 

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Code 56094 system pressure out of range, Code 56109 is operator not being seated, when was last time tranny was calibrated? would suggest this, hyd oil needs to be warmed up, I think about 60 degrees Celsius, or it won't let you calibrate it, suction screen is on bottom of tank, have to drain tank, rear end and tranny use the same same oil tank
 

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Discussion Starter · #5 ·
Scott we calibrated the tranny yesterday. Is there any way to blow in a hose to clean out the suction screen without draining the system? Could some of the oil be bypassing the transmission throught the pto? Everytime you start it you will get a different tranmission oil pressure. Sometimes 160, 180, or 200psi. If it is 160psi it will only move a foot and throw transmission faults.
 

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There is a sight glass right on the back of the transmission and the fill tube for it runs up not far from the hyd. Reservoir fill. We are talking about a Case IH 4wd aren't we? I don't know of any other stx model designations myself.
 

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The codes Scott are 56094 and 56109. Is there a screen on the bottom of the transmission? I thought the oil in the transmission was seperate from the hydraulic system.
Thanks for your help Scott.
There should be a suction screen on the trans charge pump. My experience is with Case 9280 with Fuji PS and Challenger 965 with Cat 16 spd PS. Both have suction screens in the bottom of the trans housing. Nothing to do with the hyd system. I have had weird things like floating debris that must have come from original assembly or bad service work. Bottom line is if the oil can't get to pump you will have fluctuating pressure. Fairly easy to drain oil from trans and check that suction screen. The variable pressure readings are interesting in that they could indicate something falling off a suction screen and then getting sucked back up after a time of running???Likely can wash it out or replace it for a couple hundred bucks if it has a lot of crap stuck in the screen. What about a faulty pressure sensor? Can you plumb a manual gauge to system and confirm that your pressure is actually low? The computer is only reacting to the reading that it gets from the sensor and if sensor is giving a bad reading the rest of symptoms are just a result. Beyond that it would point to pressure loss or leakage internally but I would not panick yet before checking the simple things. Good luck!
 

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Discussion Starter · #14 ·
I pulled the transmission regulator valve block off on the front of the transmission. The main pressure control spool had a slight wear or rough spot on it that was dull and not polished or smooth. I took 1200 grit emery cloth and oil and polished this area so you could not tell where it was. I put it back on and have good pressure. I will not know for sure until It dries up and I am able to use the grain cart again. It however appears the main pressure control spool was sticking or not moving properly with the magnet from the solenoid valve. I hope this fixed it. I will know better next week. Thank you for all the response.
 

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I pulled the transmission regulator valve block off on the front of the transmission. The main pressure control spool had a slight wear or rough spot on it that was dull and not polished or smooth. I took 1200 grit emery cloth and oil and polished this area so you could not tell where it was. I put it back on and have good pressure. I will not know for sure until It dries up and I am able to use the grain cart again. It however appears the main pressure control spool was sticking or not moving properly with the magnet from the solenoid valve. I hope this fixed it. I will know better next week. Thank you for all the response.
Nice detective work SouthernSK! Hope it solves your problem. I did not know there was such valve on these tractors. We can learn something every day!!. Thank YOU!
 

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Discussion Starter · #16 ·
Transaxial the valve is crazy expensive at over $5000 for a new one. The little spool I polished was close to $600 and "o" rings about 1 inch in diameter were $20 a piece from the dealer. What is the world coming to. Next they will be charging you $50 to use the bathroom at the dealership because as I was told margins are to tight on these parts.
 

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Discussion Starter · #17 ·
Transaxial this valve has a pulse modulated solenoid that slides the spool I polished. The solenoid throught the spool controls the oil flow through the transmissin to give you around 280psi lube pressure all the time. When the transmission on these tractors kicks out because it is lugging down to far or has too much torque I am pretty sure it is due to a pressure drop in the transmission in the lube circuit below 200psi. They have it kick out rather than get damaged due to lack of lube. The older series did not have a pulse modulated solenoid but just a regular solenoid.
 

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Had the same issue with my 550 this spring. Polishing things did help, but we ended up
putting a shim in the valve spring. Had a washer that fit perfect. It was about .015 to .020 thick. Took the pressure from 275 to 305 psi. No more issues
 

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Discussion Starter · #20 · (Edited)
Thanks for the great tip. QT550 i wonder if a guy could buy those little shim washers? Did your spool spool have a slightly roughened surface on it? I was wondering if the steel in it was defective. I will now be paying more attention to what the oil pressure is in the transmission when it is running.
 
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