1960s JD 4020 Hydraulic Problems

I have an early 60s JD 4020. I recently changed out the hydraulic pump (driven off of front of motor; bought rebuilt pump with warranty $1200!!) and everything worked just fine last weekend. Today, pump sounds like it may be cavitating a bit when under load (i.e. makes a grattling sound when under load). I can raise the front end loader but it goes up really slow, seems the pump isn't pressuring up enough. Hydraulic oil level is topped right up and brakes, transmission, steering etc. work fine, changed hydraulic oil filters (2 filters as its a power shift transmission) prior to starting up after changing out pump, no leaks to speak of; basically everything works good except the pump makes a noise when under load that I don't recall hearing last weekend and front end loader doesn't work properly (neither smooth nor quick) both raising and tilting the bucket. Thought perhaps it may be sucking air? There is a cooler which I believe ties into the suction side of the pump via a ~1.25" rubber hose, tightened clamps up and doesn't appear to be leaking however may be very slight leak on cooler itself but its been there every since I bought the tractor. Any other ideas?

Yay! This is my first time to be the first to say....GET A BOOK!!!!! Okay, now that that is done, a little to chew on while waiting for your new shop manual to arrive, by the way, the deere shop manual is much spendier than the IT manual, but the hydraulic section is also much better, worth the money I would say.

First off, your pump will not be sucking air, as there is no "suction" side of the closed center piston pump, it is supplied by pressurized oil from a transmission driven charge pump at between 50 and 130 PSI. Your front end loader will require more pressure to perform up to par than steering, brakes and such, so lack of performance will be more noticable, and the steering and brakes are protected by a priority valve, so if the pressure or flow is weak, it will all go to those circuits before accesory hydraulics (the loader).

It coud be your new pump is not adjusted correctly, there is a process for checking the stroke valve adjustment (in the handy book....) or you could have a valve problem in your loader, or many other things.

First thing to do is get a book, then check line pressure, then check your charge pump pressure and flow, establish that both pumps are working well, then check for leaks or problems in the system.

Josh

on my 3020 there is a screen in the bottom of the
transmission housing where the hydraulic charge
pump picks up the hydraulic oil, there is a large
hex nut cap that needs to be removed and then this
screen will come out. It is long and maybe 1' in
diameter that pulls out that hole. It may be
restricting the oil. Have to drain trans and not
much fun but might be worth a look. If you get on
J D parts on the computer the screen is part
#R53169 nylon or AR26375 steel. May not be helpful
information but relates to my experience.

I'd suggest investing in a 3000# pressure gauge and a length of hydraulic hose (can use a hose off a existing piece of equipment, if so desired); plug it into the breakaway coupler, operate the scv and and see if you have about 2250# of pressure.

What kind of loader, loader valves and how is it
connected to the tractor's hydraulics? A failing
loader control valve can cause such symptoms.
The front pump is supplied with what ever oil the
trans pump has left over. After the powershift and
pto is taken care of. Internals leaks in either will
cause grief.
What serial number is the tractor?

It's probably the coupler between the hydraulic pump and the engine. Check it. The little plastic bushing will wear and begin to make noises.

My neighbor had this exact problem. I went and
tried it and everything worked fine after a few
cycles. Then I said you try it. He got on and
started it a 3010, cycled everything and then it
started cavating again,and making these weird
sounds. All the time he had his foot on the
clutch. The charge pump doesn't turn with the
clutch pushed down. Be sure you aren't using the
loader much with the clutch pushed down. There is
a can between the cooler and the pump on our 4040
to help this. you could put one on your 4020. This
is not right if you have a power-shift. Vic

Did you clean the screen in the sump?