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John Deere 4640 Hydraulic problems

G

gunnargt95

New User
I got a 1978 John Deere 4640 Powershift with hydraulic front wheele drive.

The 3-point jerks and shakes very badly when lifted (at any rpm), and if I leave it over night with the 3-point lifted, it has dropped when i come out in the morning.

The suction screen looks good, but maybe the suction-line is plugged? New filters. But not new oil.

What can be the problem?

Thanks!
 

JD closed-center hyd's require good diagnostic procedures to determine problems. 3 pt shaking while raising could be caused by low stand-by pressure which should be 2250 psi. I suggest to acquire a gauge & check pressure. 3 pt settling could be leaking control valves, faulty RS piston seal or faulty thermal relief valve. Change position of L/D control knob located by your lower right leg when setting in seat to determine if that will affect 3pt settling.
 
   Your 3 point hitch lowering when engine not running is normal. John Deere three point hitches have designed leakage, they all settle.
 
(quoted from post at 14:38:43 08/03/21) Your 3 point hitch lowering when engine not running is normal. John Deere three point hitches have designed leakage, they all settle.
Click to expand...

I've never read what you stated in a JD tractor operators or tech manual. The 3 pt hitch on my JD 4255 will remain raised for months until I need to attach an implement to the 3 pt. For many yrs I utilized this 3 pt hitch on a 24' 1010 field cultivator.
 

A leak in the rock shaft piston seal or control valves that are out of calibration will cause the problems stated .
What kind of hydraulic oil ? If some overly economical Bubba has dumped in the incorrect oil . There will be problems .
Not unexpected or a surprise for a 39+ year old machine even if service was 100%
 
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