JD 4520

rdhRDH · Aug 27, 2018

Have a JD 4520 Powershift, steering quits when you step on the clutch, when clutch is out everything works OK, have taken priority valve apart, was not stuck, pipe to rockshaft gets warn after a couple of minutes of running. Even if there is a leak in the rear, steering should still work and why does it quit when you clutch it?

Dieseltech · Aug 27, 2018

How long are you holding the clutch pedal down? There's a rear charging pump driven by the clutch shaft that supplies oil to the front radial pump.

Bob · Aug 27, 2018

As DT says, transmission pump supplies oil to the main hydraulic pump through the oil cooler.

When you depress clutch, transmission pump stops, hydraulics continue to function using oil in the cooler and reservoir up front.

"Function return oil" is directed back to the cooler, maintaining an oild supply to the main pump.

When something goes wrong, and there's a "high pressure leak to sump" that return oil is wasted, the supply up front gets depleted, and there's no oil for the main pump (and you lose steering and other functions).

Since you've noticed the supply line to the rockshaft heats up, likely that's where the problem is.

rdhRDH · Aug 27, 2018

This is a Powershift

ss55 · Aug 27, 2018

Try asking this question on the John Deere forum below.

Bob · Aug 27, 2018

(quoted from post at 12:13:49 08/27/18) As DT says, transmission pump supplies oil to the main hydraulic pump through the oil cooler.

When you depress clutch, transmission pump stops, hydraulics continue to function using oil in the cooler and reservoir up front.

"Function return oil" is directed back to the cooler, maintaining an oild supply to the main pump.

When something goes wrong, and there's a "high pressure leak to sump" that return oil is wasted, the supply up front gets depleted, and there's no oil for the main pump (and you lose steering and other functions).

Since you've noticed the supply line to the rockshaft heats up, likely that's where the problem is.

I didn't catch the "powershift" thing, either.

Pump at the front of the transmission (much like an automotive automatic transmission pump) supplies oil to the powershift, and excess oil after regulated pressure is achieved goes up front to the cooler and pump.

Start by checking the sump screen for debris, and changing transmission filter.

If that doesn't help, pump MAY be worn/weak or something may have failed in the clutch or shift valve area that's dumping pump flow to sump when the clutch is depressed.

I would check the transmission pump flow, as well, don't have the tech manual at hand for a detailed procedure, it's at the shop.

Going back, though, if the line to the rockshaft is heating, you have a leak back there that is hastening the oil up front in the cooler and reservoir being used up. That issue needs to be corrected, as well.

JD 4520

rdhRDH

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Dieseltech

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Bob

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rdhRDH

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ss55

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Bob

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