I have a case 850 H we tested all the pressures and they are within spec until we got till the solenoid control high low range control valve High and low range are 190 psi lower than the charge pump pressure High and low range are both reading approximately 112 pounds The pressure at the Filter is 308 psi All other clutch pressures are around 297 psi Any idea what and where I should start looking for? Thank you
Here is the troubleshooting.
Which valve are they calling the modulator valve the transmission control valve or or the solenoid operated high low valve Thank you for your help
If charge pressure is 308 psi and both high and low range circuits are only around 112 psi, I'd start at the high/low range control valve itself. Could be a sticking spool, leaking seals, weak solenoid, or an internal leak in that circuit. Since both ranges are low by about the same amount, it seems less likely to be a clutch pack issue and more likely something common to both circuits. I'd also verify the solenoid is getting full voltage and check for any restrictions or contamination in the valve body.
Here is the Hi Lo breakdown. Blocked screen #20, or as stephenrobinson check the solenoid, o rings.
Update I have taken the solenoid valve apart. I cannot find anything wrong with it. Change the O-rings and backup rings I’ve messed with the springs. And cannot change the pressure. Also checked the pressure going into the valve and I get about 285 only getting about 130 to 140 at at the test port Could I be losing that much pressure internally? The bad part is the valve is no longer available through case going to start looking for a used one Thank you, everyone for your help
You need to isolate LH & RH / HI & LOW Have you taken a pressure reading with the HI/LOW pipes removed & capped? (instructions in the test proceedure posted by gggraham) The teflon oil control rings on the shafts, maybe the cause of your problem. If they are damaged & allowing pressure to both HI/LOW while operating the machine - over long periods of time, the clutch packs could be damaged. Unfortunately, the 850H does not have shaft end caps that can easily be removed to visually inspect the shaft seals......stupid idea...... (people get paid alot money to redesign a perfectly good set-up from older models & make it somehow more complicated & better?????)
We think our problem is in the high low range solenoid valve We put the machine to work. It does OK with 125 psi we’re running out with the gauge on so we can see what’s going on Periodically gauge will drop to 15 or 20 pounds in the machine will not move We found if we remove remove this the pipe plug from the solenoid valve and take out the spool and then put it back in. We get our 125 pounds back. We’re thinking this is sticking or something and not letting the pressure build going to the clutch pack We know one of the springs and there did not meet the spec in the manual. We stretched it out to get it back to spec, but have not found a replacement yet I can’t believe we have a problem internally in the transmission. I would assume that once the pressure dropped a seal or a O-ring went bad. It would not come back later on.? When I had it in the shop, I found that if I shimmed the heavy spring that is on the right hand side of the valve to push the spool to the left just the tiniest bit. I had no pressure. Have not figured out how to shim it to the right yet to see if that changes the pressure
I remember the first 550H with the clutch packs blowing apart because they were just stamped steel. Then the big update was the same drums with a ring welded to them. They still would get slotted and clutches didn't perform well. The good old cast drums were far superior.
Yes, we first saw that problem here in the 850E's - I would have thought the H's would have had the drums with the welded rings fitted from new...... But maybe some early H serial numbers missed the memo....
Sounds like there’s a lot going on with this machine. Has anyone checked the seal rings in the rear cap where the hi/lo shaft come out of the transmission case.