3 pt Bushhog backhoe PTO pump or hydraulic relief ??

[evojohn]

Backstory: I have a JD 3720 hydrostatic open station, added the power beyond hydraulic ports as suggested by the dealer. I'm using a Bushhog 765 3 point (not frame) mounted backhoe and it's functional, HOWEVER, the tractor HATES the backhoe. The hydraulic pump whines and is obviously burdened by the backhoe. When I'm moving to the dig site, I feel like I have to constantly operate the FEL bucket to relieve pressure and the pump and motor sound like they appreciate it. The tractor will operate if I don't but it sounds bad to me. I took it to a not local dealer, farm based instead of the closer urban lawn mower dealer, and they said it's fine but it feels like I've lost lifting power over the last year or so, possibly due to over-burdening the pump. (I've also noticed my FEL bucket doesn't stay in position, probably need cylinders rebuilt, but...) It's got just over 1200 hours but I've been using it pretty hard to clear an acre of trees and build my 40x80 shop/barn.
I contacted Bushhog about getting a PTO driven hydraulic pump. It seems a little odd to drive a hydraulic pump from a hydraulic motor driven by a hydraulic pump but at least the systems would be isolated from each other. Unfortunately the pto pump kits are no longer available.
Now the actual question: Are there other options? pressure relief/bypass? where to source a used PTO pump?

 

[oldnslo]

How many lines or hoses are connected between tractor and three point?

Does back hoe operate properly?

What you describing sounds like possible problem on how the back hoe valve is configured or connected.

 

[404nouser]

Is it set up as closed center or open center?
And your tractor is open center, but some old Deere's are closed center.
If it's set up for closed center your tractor won't like it and it'll be on the relief valve constantly.

 

[Jstpssng]

I wouldn't use it until you get this resolved. Replacing an internal pump can be a PITA.

 

[evojohn]

Oldnslo there are only 2 houses connected between the tractor and backhoe, both by quick disconnects. Pressure from the pump and lo/ no pressure return. When the 'hoe is connected I have to disconnect a "loop" hose from the tractor that disables my 3pt lift arms. Is there a way to create a pressure relief/ bypass for this?

 

[evojohn]

Is it set up as closed center or open center?
And your tractor is open center, but some old Deere's are closed center.
If it's set up for closed center your tractor won't like it and it'll be on the relief valve constantly.

Based on operation, it's closed center, the tractor hates the backhoe. When I bought it, it came with what appears to be a relief valve (pic attached) but neither the seller nor the local JD dealer tech (maybe 20yr old, I think the parts are older than him) knew what it did or how to set it up. And surprisingly, the internet has no info on the relief either, probably it if business before Dan invented the interwebs.

 

[404nouser]

You are probably going to need to find out how to convert to open center valves.
Or buy a closed center tractor.
I put a loader joystick in a 4020 and had to buy the closed center adapter for it.
I purchased both the adapter and joystick from summit hydraulics.

 

[Sportsman762]

Not sure if I can help with the hydraulic issue. But the photo that @evojohn posted shows casting number 2818. Based off the ID guide below it is a Gesen WJL relief valve.

https://www.parker.com/content/dam/parker/msg/hydraulic-valve-systems-division/PDF-files/bulletins_brochures/Parker_Gresen_Casting_Identification_Guide.pdf

Here is the info for the WJL relief valve on page 16.

https://www.parker.com/content/dam/parker/msg/hydraulic-cartridge-systems-division/PDF-files/catalogs/legacy/gresen/1985-Accessory-Valves-PC-4000-Combined.pdf

If the main valve is a closed center that is causing the relief valve to open up. This would put considerable strain on the hydraulic pump if it is pumping all its flow at max psi through the relief valve instead of the normal unrestricted flow to tank. I think that 404nouser is onto something.

If it's set up for closed center your tractor won't like it and it'll be on the relief valve constantly.

If you can find some info on the valves such as castings numbers or data plates the pdf's I linked above might help you ID what you have for a valve.

I found a manual for the backhoe.

https://ia801908.us.archive.org/21/items/manualsbase-id-665785/665785.pdf

Page 25 to 27 of the manual discusses the hydraulic setup. The relief valve you show is on the closed center system or setup for surge relief on an open center system.

 

[hayden]

The backhoe manual shows the various hydraulic hookup arrangements starting on page 25. Something in your setup isn't right.

With your bypass hose installed, everything on the tractor should work correctly and normally.

With the backhoe hydraulics connected, everything on the tractor should still work just as though the backhoe wasn't there. If it doesn't, which is what you are saying, then the hookup isn't correct and that's the place to focus.

I agree with others that it sounds like one machine is set up for open center hydraulics and the other is closed center. I'm not familiar with your tractor so don't know which it has, but the BH needs to be set up to match the tractor's hydraulics. Actually, I think a power-beyond is unique to open center hydraulics, so that answers the question about your tractor.