Hey bama-mill, I keep forgetting to contact my Deere dealer when I get to work. (banghead). Sent myself an email reminder to do it first of the week.
But let's go over what we know about the machine. We know it's a closed center hyd circuit and should have around 2,300 lbs standby pressure on the pump output line when no functions are being operated. We know the pump has been replaced and caused no change, so it's least logical to be a pump problem. We know we are generating heat, most probable cause is internal passage of oil around a failed component or seal. All we have to do is find where the leakage is happening. First, though, have you put a pressure gauge on the pump output to verify standby pressure? Moving on, it would be nice if we knew how the fluid routes on your machine. If it's anything like the 410 circuit, fluid leaves charge pump to feed main pump (I know you've said it does a reverser connection in here, but it sounds like it's working properly), leaves main pump to feed priority valve. It goes several directions from here; loader valve, backhoe valve, steering orbit valve, aux valve (if equipped), and main pressure relief valve going back to charge pump circuit. That "relief line is the first line I would feel for getting hot. But if you don't want to take the time to wait, take this line loose from the priority valve and plug the hose fitting. It would be nice if you had a hose you could put on the priority valve fitting and drop the hose in a bucket. Start the engine, there should be no oil coming out of the priority valve fitting. Do the same to the other valves. Locate the "T" port fitting (the return line going out of valve body). Plug the hose fitting, run engine and see how much oil leaks out of the T port. A very very small amout would be acceptable, normal leakage around spools, but it should be a very small amount, not even a little stream. I know it might be a pain to do some of these valves, but you should be able to narrow down where the problem is by doing this.
