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Faunsdale, AL | There was a fix for that on the older tractors, but the side console tractors should not do it unless there are high pressure leaks to sump that are loosing oil from the return circuit back to front pump.
Transmission charge pump should replenish any leakage from high pressure system by adding about 7-8 gpm of oil drawn from sump through the screen. Most of this oil normally goes through front pump, out the top and up to surge reservoir tank by radiator, through oil cooler and returns to transmission sump cooled.
When there’s leaks in the high pressure part of the system, they may be leaking to trans sump, so the limited trans pump flow is used replenishing this loss from the circuit and less or none goes through oil cooler depending on how bad the high pressure leaks are.
As soon as you push the clutch in on the synchro-range tractors, the trans pump stops and the tractor starts using oil accumulated in the tank in front of radiator that’s on the later tractors. Once this is gone supplying the front pump to push oil out through the leak(s), the front pump begins to chatter.
It’s possible the trans pump is shot, but it may not be, instead the problem may be high pressure leakage in steering, pressure control/priority valve, rockshaft or SCV’s.
Rock shaft housing has a bolt-on cover plate on the bottom that keeps return oil from SCV’s and maybe rockshaft control valve in the return circuit instead of it dumping to the sump. If you have rock shaft housing off, check that gasket is not blown.
SCV’s and rockshaft sometimes make noise and will get hot too fast when they’re leaking. Rockshaft would usually settle quickly as soon as engine is stopped if the problem is a blown piston seal or outlet valve poppet. If it’s leaking, it should heat up too quickly with tractor running but not using the rock shaft. Lift cylinder should get warm too. Does it make any difference if the rockshaft control is lowered all the way?
Do you have a loader with a separate control valve on it? It could be the leaking high pressure component.
Edited by ccjersey 12/1/2022 20:14
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John Deere 4020 / Transmission Hydraulic Pump
