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Faunsdale, AL | First, is it a synchro-range with a real clutch or a power shift with an “inching pedal/clutch pedal?
I’m assuming it’s a synchro. So when you push in the clutch on the smaller synchro tractors, the transmission input shaft stops turning and so does the transmission/charge pump. 5020, 6030 and 30 series and later tractors aren’t affected because they have a driveshaft from the engine crankshaft through the clutch to drive the charge pump at all times.
On your tractor once you push the clutch in, there is only a limited amount of oil in the surge tank and oil cooler up front by the radiator to make up high pressure losses to sump. Normal use of the SCVs with the return hose plugged into the coupler along with the pressure supply hose keeps oil return in the circuit going forward…….or it’s supposed to. There are some scenarios where it can leak away into the rear housing and then it’s not available again until you let the clutch out.
Basically anything that uses or leaks high pressure oil and does not return it to the charge pump circuit going forward to front pump is going to deplete the limited amount of oil that can gravity feed the front pump to supply any demand for high pressure oil.
Priority valve can leak to sump I think and it’s supposed to keep steering and brakes running longer by shutting off flow to SCVs and rock shaft. So if it’s not functioning, you’ll loose steering at the same time as everything else. Steering, brakes, pto and rock shaft are all possibilities for high pressure leaks. Pretty much have to cap off each in turn and see what effect it has on the loss of hydraulic function.
I have a 4320 with a front end loader on it. We had been using the SCVs to operate the loader and it was pretty awful to chatter trying to load bales etc. I bought a cheap loader joystick valve and installed it with supply from
Power beyond source and returned oil to a ported filter cover I had around. That made a new tractor out of it. It should not have had to have the ported filter cover return but I had it, so I used it. | |
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JD 4020 Hydraulic Problems
