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Faunsdale, AL | It’s normal to loose hydraulics………. eventually.
Problem is those tractors are all about 50 years old now and very few of them are still as tight as they were when they rolled out of the factory. So, it may be normal to quickly loose hydraulics when you push in the clutch……now……but it should not IMMEDIATELY start to chatter if it’s in good shape.
Some flow tests would help. I would start by removing both SCV’s and installing block-off plates if possible. Use rockshaft lift to test how the hydraulics perform. Or you can do one at a time if you have to have one for a loader etc.
I improved my 4320 a lot by adding a loader valve on power-beyond pressure with its return plumbed to a ported trans/hydraulic filter cover. I had been using the SCV’s. I can only assume the return from the SCV’s was getting lost to rear sump instead of staying in the charge pump-filter circuit like it’s supposed to. I actually had the rockshaft off last winter and forgot to flip it over and check the cover plate and gasket that keeps the return oil in.
The other possibility is there is a valve that you can open that dumps the return flow from one or more SCV’s to sump so that light loaded single acting cylinders won’t be held extended by the charge pump circuit pressure. If that’s open, any leaks through the SCV’s or return flow from actuating one of them is lost and with the clutch pushed in, it’s going to chatter pretty quick.
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John Deere 4020 / Transmission Hydraulic Pump
