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John, Technician
Category: Heavy Equipment
Satisfied Customers: 135
Experience:  20 years in a John Deere; Ag,Ind,forestry and Bobcat dealership,12 in my own shop
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I have a John Deere 4020 that lost all hydraulics. I changed

Resolved Question:

I have a John Deere 4020 that lost all hydraulics. I changed the fluids, filter and cleaned the screen and still nothing. Any thoughts as what to check next.
Submitted: 7 years ago.
Category: Heavy Equipment
Expert:  John replied 7 years ago.
Hi Monty

There is a little valve in the front hydraulic pump that controls the pressure and sometimes the seat gets bad and it will not allow the pump to build pressure. Called the stroke control valve. It is a little tricky to replace in the machine , but it can be done. But before replacing I would try to use this special tool, have to get from JD, AR33249 is the part # XXXXX It is called a destroker. on the left side in front of the radiator is a plug that goes into the top of the pump, takes a 11/16 wrench. remove that plug and install this destroker. start the machine and turn down the destroker screw until it starts to turn hard and then go 1 turn more. let it stay down for 20 seconds and then back out the screw. most of time you will hear the pump kick in and start pumping. if it doesn't try screwing it down again. When you buy the part from the dealer they will be able to explain it also. I have had many of these go along time without having to replace the valve.

Thanks John

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Customer: replied 7 years ago.



Here is a little more information. I was running the tractor and started to lose power in higher gears. I stopped for the day and checked fluid level. The fluid level was a little low. I added to it to bring it up to full. Next day when restarted, thats when found there were no hydraulics.



Expert:  John replied 7 years ago.

That goes with what I told you. It seems if the oil gets a little low sometimes it will do that.

Is this a syncro or a powershift?

Thanks John
Customer: replied 7 years ago.
Its a syncro