I have a 76 IH 3500A backhoe with some hydro issues and am hoping someone can help me out. I've checked the charge pressure and the servo pressures, and both are ok. A high pressure gage on the high pressure line really shows nothing so I tried a low pressure gage. It's about 210 lbs all the time, which is what charge pressure was. The tractor is intermittant. Sometimes, it won't move at all forward or backward, doesn't even try. Next time you get in, it moves just fine, has plenty of pushing power doesn't slip at all, works great. Shut it off for a minute and start it back up, it won't move. I eliminated the foot-n-inch valve thinking it was dumping pressure after the restart, sticking because it has to be applied for the neutral safety switch to close for cranking engine. I pulled a small plate off and ovserved the pump servo when running and it moves as commanded. Anyone got any ideas? I'm fresh out. Orderd a manual but haven't received it yet. If anyone has any idea what might cause this, I would greatly appreciate any input or idea you have. Thankyou. Kim
low charge pressure 210 for charge pressure sounds a mite low-I believe you need to be around 300 psi. I don't have a manual either but am drawing from memory for IH combines and cotton pickers that were similarly equipped. If your charge pressure is too low the pump swash plate will never move generating no flow. Intermittent problem could point to a bad low pressure relief, stopped up filter. Hope this may help, Maytag
I dug out an old service manual for the IH combines/cotton picker hydrostat drives. Charge pressure should be 120 @ low idle minimum 160 @ 2500 rpm when main pump and motor are under load minimum 180 @ 2500 rpm when hydro is in neutral
My charge pressure is 210 lbs, and my servo apply pressure is 360lbs. I watched the servo stroke so I know there is enough pressure to move the swash plate. The specs. I got are 180 to 240 for charge, and 390 to 430 for servo. so my charge is in the middle of spec. but the servo apply is a little low, but it strokes the servo so my guess is that there is enough pressure. There is also 210lbs pressure in the high side line, charge pressure I assume, so I know it's getting to the hydro pump. Something has to be stuck open preventing the hydro pump from building pressure. Without a hydraulic schematic it's just a guessing game. Waiting for a manual, no idea when it will be here. Hoping someone might have one so I can track the circuit. Thanks for the help. Kim
Well it's fixed. With the help of others on here I found the problem, a stuck high pressure relief valve in the reverse side. Replaced it, and it works like a charm. Thankyou to everyone involved. Kim
Hydrostat repair I have the same unit with the same symptoms, no too familiar with the setup. Can you tell me where the pressure relief valve is located, and did you just clean it or replace it ? Thanks Lee
Did you get it going? Sorry I never got back sooner. Send me your email if you want and I will tell you as much as I know about the unit. Kim
3600a Hi, I seen your thread here and was wondering how the machine is doing? Is it still working. I just purchased a 3600A with no forward or reverse. These seem to be great machines when working properly. I am having trouble finding parts for this and a parts diagram. I have a manual for the hydrostatic drive from the Case website. Could use a parts manual for the entire machine.
Just got the manual a little over a week ago and I haven't had time to look at it yet. My local case IH dealer has been able to get any part I have needed so far.
Just figured out what was wrong with my drive. The valve stop on the foot n inch valve was broken. It connects to the neutral safety start pedal and dumps all drive pressure when depressed. When it broke it stayed in the open position. I am now trying to find a replacement - if I can't I am going to weld it. Hope this helps.
Really? I am going to have to take a closer look at mine. So far by the slimy hydraulic filter and all the water in the fluid, I am leaning toward this as the problem for my drive issue? However am listening to any suggestions and giving them a try as to troubleshooting the drive issue. I am still debating doing a complete restoration on mine. Very Solid machines. Any suggestions are appreciated.