L35 hydraulic clutch replacement still no pressure to pilot circuit

[chromeaholic95]

Hello all. I'm new to the Orange tractor talks, but am not new to the workings of the L35 kubota GST.

I brought an L-35 into my shop for repair (would not move) . Found the Hydraulic clutch was broken, and metal and material were all over inside the case. Split tractor and replaced the manual clutch and the Hydraulic clutch and the Shuttle shaft, 2 shifters and pins. cleaned everything up and put tractor back together.

Fired it up and had no movement of tires. Got out the Pressure gauge and found GST has 350 psi to it. steering and hydraulics work. Check the Pilot circuit as in WSM page 3S51. no pressure at all. drained the oil again. used a blow nozzle on the hydraulic clutch to see if it locks up. it does, but I can still hear air leaking from what appears to be the mating surface of the hydraulic clutch to housing around the 2 oil rings. Is it ok if there is a little leakage of air when testing the clutch?

used compressed air to make the GST Valve operate. works like it should and moved shift shafts to proper location. have checked the modulate check valve, modulating valve, and pilot orifice for debris. appears to be correct. what else can I check to see If there is something else going on with the GST valve?

 

[North Idaho Wolfman]

Is it ok if there is a little leakage of air when testing the clutch?

used compressed air to make the GST Valve operate. works like it should and moved shift shafts to proper location. have checked the modulate check valve, modulating valve, and pilot orifice for debris. appears to be correct. what else can I check to see If there is something else going on with the GST valve?

Yes you will get air leaking out of the clutch pack, It's not air tight, it takes fluid force to seal the rings.

I'll have to look at the schematics to get you better answers.

One thing to check is the position of the rotary shifter valve, 180 degrees out will cause it to not work properly.

 

[chromeaholic95]

That's what I was hoping for on the clutch pack. I noticed that all of the accumulators and modulators still had contaminated oil in there. Ive taken most of the GST valve apart and cleaned it. Except for the clutch valve, and low pass valve. that will be either today or tomorrow.

 

[chromeaholic95]

I did check the orientation of the rotary valve and it is in the correct spot with the detents facing each other in neutral.

 

[chromeaholic95]

I checked everything in the GST valve and found that if I put the transmission in 1st gear when installing the GST valve, it will move and has pilot pressure like it should. it also shifts into high range 5. Problem is it will not shift into anything but 1st and 5th. When I first started to pull everything apart it was so contaminated you could barely see the bolts from clutch material coming apart. I'm leaning toward a rotary valve leak that is not supplying oil to the shift pistons to actuate a gear shift. this GST is getting more expensive the further I go. anything else I can try before buying parts?

 

[North Idaho Wolfman]

Sounds like the valves or ports in the valve body are plugged up, shouldn't have happened as the fluid feed to them should have been completely filtered before it got to any of the ports or valves.

Or you might not have a O-ring or several not in it right, the valve bodys can be tricky to seal to the cover.

 

[chromeaholic95]

I just got back into the shop (after Christmas and New years) and disassembled the rotary valve again and cleaned both sides. tested with air, and it shifts like it should. reinstalled in 2nd gear and refilled the case. shifts into 2nd and 6th, but nothing else. how far does the pressure have to drop in the pilot circuit to initiate a gear shift, then a clutch pack engagement. I have a WSM and it doesn't state what should happen next. Thanks for your help ya'll.

 

[North Idaho Wolfman]

I just got back into the shop (after Christmas and New years) and disassembled the rotary valve again and cleaned both sides. tested with air, and it shifts like it should. reinstalled in 2nd gear and refilled the case. shifts into 2nd and 6th, but nothing else. how far does the pressure have to drop in the pilot circuit to initiate a gear shift, then a clutch pack engagement. I have a WSM and it doesn't state what should happen next. Thanks for your help ya'll.

So the clutch pack is working along with high low valve, it's just not operating the shift valve.
It doesn't sound like a pressure issue as it wouldn't move at all if the pressures were not right to be able to engage the clutch pack.

How far have you gone into the side cover and valves?

 

[William44]

Hi, i have the exact same problem with my L35 only 2nd and 6th shifting after dissambling the transmisson for a foward/reverse clutch rebuild but everything else works fine… did you came with a conclusion on your?