JD 350 CRAWLER/LOADER/BACKHOE

[Bill Fortune]

JD 350 CRAWLER LOADER/BACKHOE has Drot (spelling ?) 4-way bucket. Main relief is opening at 800 psi (rated 2250), new hydraulic pump. need main relief valve or a way to repair it. It appears to consist of two pieces, but unable to take them apart. The relief I see in the SM-2063 Service Manual (Jan-1974) is not exactly the one I have.
Tractor S/N; T21358T

 

[Dave M7040]

JD 350 CRAWLER LOADER/BACKHOE has Drot (spelling ?) 4-way bucket. Main relief is opening at 800 psi (rated 2250), new hydraulic pump. need main relief valve or a way to repair it. It appears to consist of two pieces, but unable to take them apart. The relief I see in the SM-2063 Service Manual (Jan-1974) is not exactly the one I have.
Tractor S/N; T21358T

Sounds much more like a hydraulic valve for something is not in the center position is draining off pressure.

Open Center of closed center system...?

Dave m7040

 

[Tx Jim]

Bill
Welcome to TBN
My JD industrial equip.knowledge is very limited. Although I will guess a JD 350 crawler has closed-center hyd's I couldn't confirm it. Can you please post a photo of the hyd pump? Keep in mind many hyd pumps have been replaced only to determine original pump wasn't the problem. I would think any 2500# relief valve could be made to work. Original pressure control valve is still available from JD but one needs to check pump pressure 1st. If frt pump is CC then problem could be that stroke control valve in pump isn't seating properly. Has hyd filter been changed lately?

AT18944 Pressure Relief Valve ADD 323.83 USD

 

[Bill Fortune]

It's a "pass through" body, open center valves. I thought that the old pump was having a problem, but the new pump is not any better. I think I see that each or most of the control valves have a relief also. I had to take the bucket off and use it only as a backhoe. I could re-pipe the system so to eliminate the Main Relief, but would lose all control of the bucket boom and dump cylinders.
All valves are held in center. Centering springs are ok.

 

[Tx Jim]

Does your 350 have a gear or piston hyd pump?

 

[Bill Fortune]

can't post pictures just yet, have a new "smart" phone that is a pain the system relief is built into the valve body so a plug would have designed. also see my comments to TX JIM

 

[Tx Jim]

It will surprise me if 350 crawler has open center hyd's.

 

[Bill Fortune]

OK, I think I see what you are saying. When the valves are in the neutral position then oil is trapped so the cylinders can't move. So I will se if I can find the "circuit relief" valves. Maybe there is a spring in one of them that is broken. Or why can't one of the Anti-cavitation Checks be broken, but if that were the case wouldn't a cylinder move ? Another observation. With the bucket dump cylinders removed from the bucket the pistons don't move in or out (???). I will try again to make sure.

 

[Tx Jim]

Bill
Do you understand the differences between closed & open center hyd's? When a hyd control valve is centered no matter if it's CC or OC cylinder should stay in that position if control valve or cylinder aren't leaking internally. What are you referring to as an anti-cavitation check? I sent you a PM
Jim

 

[Bill Fortune]

gear pump