447 backhoe pressure relief valve adjustment

[jd670]

I just realized I first posted in the lawn & garden thread. My bad. Has anyone tried to adjust the relief valve setting on a 447 backhoe to give it more power? My JD manual says its set at 2250psi. I know the 448 hoe is set at 2550psi. On paper it seems a lot more powerful. I know its physically larger than the 447. I didn't know if the valve was fixed or adjustable. I've seen on YouTube were some of you have either added a shim kit or turned a set screw to increase loader pressure. Just looking to get a little root ripping ability.

 

[Harry in Ky]

Just curious, but what is the actual pressure you're working with right now? Regardless of what your manual says it is.

This is a backhoe attachment, yes/no? if so, then where does the flow and pressure come from? The tractor system?

 

[beenthere]

Have a pressure gauge that you can hook into the system? give us existing pressure at least.
This on the 3320?

 

[jd670]

Yes, backhoe attachment. I have a pressure gauge on order to test my pressure from tractor. I know from past experience with the backhoe, when new, I could stall it out on tree roots. It works fine and has good digging ability. I've done a lot of work with it with no issues. I was mainly wondering if anyone had boosted the pressure and if it made a difference. The relief valve is on top of the manifold to the right. It looks like it has a jam nut with an Allen head screw in the center. I haven't messed with it. I have a really big job coming up. Over 300 feet of water line up hill and thru a wooded area to dig. I bought it new in 2005 along with a 4210 tractor. Since then, I've upgraded to the 3320.

 

[beenthere]

Tree roots can/will stop the largest excavator, no matter how big. The relief valve is there to limit damage to other parts. But your expectations may vary, and do wish you well.

Watch the videos from letsdig18 and see those roots push the limits of his big Volvo excavators. Might see some good techniques to use as well.

 

[jd670]

I just tested the loader svc with a kit I got off ebay. Nice kit. Here is a pic of the kit and the setup I used to test. I got 2800psi when lifting the loader arm up and 3000psi when back to the ground trying to lift front end of tractor up. So I'm guessing relief pressure is 3000psi. Or, it may have been 2800psi both times. There was a bubble right where the needle was pointing. So I'm happy with the pressure there. I'll test backhoe pressure later this weekend.

 

[Harry in Ky]

Pretty neat kit. What do all those adapters fit? Assuming they are adapters.

 

[jd670]

It's a maintenance hydraulic test kit. The adapters are for different size valve, cylinder and pump hookups. Metric & SAE. I had to buy the 1/2" elbow to connect to the quick coupler separate. $5 from TSC. Kit was $52 to my door from EBAY. So far, I like it.

 

[Harry in Ky]

Yes, but is there a list of what styles/sizes of fittings the adapters fit? My problem is that with all the different fittings used today, I never know which one I'm dealing with until I take one off. At one time If I had adapters for NTP or J.I.C. I could get into most any system. Those days are gone. Now I need a forty lb box of fittings and adapters, and more often than not I still have to run to town for something else.

 

[jd670]

True. I understand that. The fittings are all NPT. 1/4" to 3/8" and 8mm -14mm. That's why I had to buy the NPT to JIC elbow to fit the quick coupler to plug into the loader SCV. I bought the smallest kit listed. They had others with more fittings and adapters. More money tho. There was a list of what each fitting and manufactures they fit in the add. If I would have connected to the cylinder line on the loader, I don't think I would have had to buy the adapter. I just didn't want to take anything loose. For my needs. this kit will work fine. From Winchester I see. Been there a few times to work on strapping machines at a printing company there. Name escapes me at the moment. That's what I do. Work on strapping machines. Bunn string tyers, pallet wrappers, scrubbers and conveyor systems. That's what the company I work for does anyway.