John Deere 4640 problem Main Hydraulic Pump

John Deere 4640 problem Main Hydraulic Pump Problems

I have 1979 John Deere 4640 which I use for a variety of tasks including planting. I have a Model 3200 Kinze 12 row planter with an orbital motor driven centrifugal pump for liquid starter fertilizer and I have a choice of either a variable capacity hydraulic population drive or a factory ground drive chain drive which I use simply because the hydraulic output is 4640 I believe has never been so great. Raises and lowers the planter and hydraulic markers slower than I would expect, even if I am not using a liquid starter when planting soybeans. This pump does not appear to be taking a large flow of hydraulic oil to operate it. Here are the details when the hydraulic system was last checked when the tractor underwent major repairs 3 years ago. 18 gpm at 1000 psi and 12 gpm at 2000 psi. The standby pressure was 2000 psi and was raised to 2300 psi.

My question has 2 parts. Are these volumes not cited too low? I guess I’ve seen something with a 4640 rated hydraulic flow of around 20 gpm, but I can’t recall any more information on that. My second question is whether these numbers are relatively close to where they should be, I saw a reference to a possibly larger main hydraulic pump that could be installed on this tractor. Is it something that can be done? Pros and cons of it?

In the final thought. The numbers I have seen for the hydraulic flow requirement for a centrifugal pump are around 2 or 3 gpm, and each of the two variable speed hydraulic drive motors is between 2 and 5 gpm. If I want to make the most of this planter’s hydraulic capabilities, would it simply be best to buy a PTO driven hydraulic unit to operate these devices and leave the rest to the tractor’s hydraulic system?

I struggle with this because it feels like the main hydraulic pump is not delivering what it should.

Remove the rear plug from the rear of the crankcase. Look for the oil that flies there, there is a lid on the bottom of the rock shaft that can blow up the gasket, thus dropping the oil back into the pan, causing the oil to flow low.

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