Loader 1972 JD 300 backhoe and loader-hydraulic problem

[bpperk]

Local cemetery has this tractor with a leaky loader control valve. Shop states that the valve is worn and not repairable. What valve will work as a replacement?

 

[beenthere]

:welcome:
Have you tried pulling the valve spools out to see if there are 0-rings that can be replaced? Some have them, some don't.
Are there two handles or one joy stick?

 

[ctlguy]

2 different loader for this machine. The 7300 and 7320 loader. The 7300 had just a conventional remote mounted valve that should be easy enough to get an aftermarket valve if the leak is too much. Not much you can do with that valve other than toss it. The 7320 used a setup more similar to later model units that have a stacked valve formation but again not much you can do with those either both valves where class fit (individually matched spools to valve housing) but parts are still available although very spendy. Is the unit expensive vs the amount of oil it is losing?

 

[bpperk]

I need to know, find out or be told, what the flow and pressure that this loader is designed for. That way I can get a proper replacement. Thanks for any help that you can offer.

 

[bpperk]

The valve is worn so badly that it cannot be rebuilt.

 

[bpperk]

This is a joy stick control. We tried a replacement valve (generic) that a local hydraulic shop supplied. The flow seems to be restricted. We tried the new valve in open center mode and closed center (power beyond) mode with the same result. How any gallons per minute does this sytem have the capacity to displace?

 

[ctlguy]

This is a closed center system. Hyd flow when new should have been about 18 gpm, 2250 psi max.

 

[bpperk]

I had this system checked out today at a reputable truck repair shop where they have the ability to check pressure and flow. They state that the original equipment valve, tested on the tractor, flows 22 gpm at 2900 psi. Also that this is a open center system. The JD manual that we have for this unit states that the valve has two relief valves. One is set at 1500 PSI and the other at 2750 psi. Could this mean that the flow throught the valve is through the 1500 psi circuit and that when the lever actuates a circuit the valve changes to the 2750 psi relief? I appreciate everyone's help. There are no JD mechanics around here that are able to remember how this system was designed. Thanks

 

[Tx Jim]

I had this system checked out today at a reputable truck repair shop where they have the ability to check pressure and flow. They state that the original equipment valve, tested on the tractor, flows 22 gpm at 2900 psi. Also that this is a open center system.

The truck repair shop is incorrect. There were no open-center hyd JD 300's built. All were closed center. Normally 2400 psi is the maximum the stand-by psi should be set or seals/o-rings will begin to blow. This is from Tractordata.

Type: closed center

Capacity: 10 gal [37.9 L]
Pressure: -unknown-
Valves: 1 or 2 optional
Total flow: 6.5 gpm [24.6 lpm]
13 gpm [49.2 lpm] (optional)
23.5 gpm [88.9 lpm] (optional)

 

[bpperk]

Now it is getting interesting. The parts book for this loader on JD 300 tractor with 7320 loader (PC-1111-(May-69) shows one relief valve. The JD operators manuel for the JD300-A and JD400-A (OML27245 Issue A1) shows a picture of the valve for the 400 series and states that the valve has two reliefs. Are the 300 series and the 400 series valves the same?

In your previous post you give values that are considerable different from what the truck repair garage determined. From what source did you get those values and is there more information with that source or reference that would help me??