Kubota L48 hydraulic quick connects for backhoe - can they be used to power 3PH hydra

[rScotty]

Thanks for the explanations. My L48 also has 3 QDç—´ for the backhoe. I am a complete novice with hydraulics. I think I understand what youæ±*e saying regarding the 2 QDç—´ that operate the digging action of the hoe...that one is the supply from the pump and one is the return. And what you said about downstream cylinders not working while the top link cylinder is actuated makes sense to me too.......because fluid operating the top link cylinder returns to the pump and never makes it to downstream cylinders, is that correct? I think I remember reading that one advantage of the L48 over other compact TLBç—´ was that it had 2 pumps for the backhoe so it could operate with a more complex motion ......closer to that of a full sized backhoe......than compact hoes with only one pump for the hoe. That 3rd QD supplies the hydraulics to swing the boom. If...if I wanted to add a second cylinder for a true top & tilt, could I do that using the 3rd QD? But I don稚 understand why there is not a 4th QD that would return fluid to the pump when swinging the boom. If there is a quick explanation that won稚 take too much of your time, I壇 greatly appreciate it.

What you want to do can be done in several different ways.

Probably one of the easiest is to simply divert flow using a T from the front remotes. This is easily done by several methods. Keep in mind that when you put a T in an open flow hydraulic system you are creating an alternate path in a system designed to feed all the flow into a whichever path is less restrictive. So the path not used needs to be either blocked or restricted. This can be done by a manual switching valve, by a priority valve, or even by the hydraulic control valve that you use to operate the cylinder itself....but only if that control valve has a "power beyond" option and the plumbing is done properly. Return hose diameter is important for long runs.

It is important that the flow path that you choose to use must have it's own valve as well as proper return paths both from the valve and from the working cylinder.

I'm sure that something similar could be done using those attractive rear mounted quick disconnect backhoe pressure/return connections for digging and swing flow..... but I don't know which is what with those rear connectors and would be reluctant to do it myself without first studying the system and then drawing out a flow diagram showing EXACTLY what I decided to do. But there's not a reason in the world why you can't do it.

I recommended looking at the front remote first because it is a simpler single system with more than enough flow and only costs you a little more in hose length - hose which you would probably want to use anyway to get the control valve forward where it is more accessible. Remember that return hoses are generally larger diameter than pressure feed hoses

I think you would find it an advantage to get the Kubota workshop manual for you L48; & advise everyone who enjoys tractor mechanics to invest in the manufacturer's workshop manual.
I have one for our M59 and it has an excellent chapter on the hydraulic system with good illustrations. One for the L48 would probably answer all of your questions.

Another thing that will help is to learn how to read a hydraulic flow diagram in schematic form. The workshop manual has that diagram as well. If you simply sketch out your proposed hydraulic circuit in schematic fashion it is hard to go wrong.
rScotty

 

[aczlan]

Excellent point rScotty, looking, it appears that they may switch both pumps to flow through to the tank or the 3 point.
Looking, the loader valve appears to be mounted on the loader tower. If you count the hoses on that valve, there should be 7 hoses on it. You will want to follow the ports marked T and PB and with a Power Beyond valve, run the PB line coming off of the loader valve into the Inlet of the new valve, a line from the PB port on the new valve to where the current PB line from the loader valve ends up and adding in a tee to the T (for Tank) and run the line from the Tank port on the new valve to the tee.

Then the excess high pressure flow from the Loader valve will flow through your new valve and into the selector valve (which chooses if it goes to the 3 point valve, or the backhoe valve).
Low pressure return to tank will then go to the tank hose and not have to go out through the backhoe or three point hitch valves.

Aaron Z

 

[jgoodma1]

Excellent point rScotty, looking, it appears that they may switch both pumps to flow through to the tank or the 3 point.
Looking, the loader valve appears to be mounted on the loader tower. If you count the hoses on that valve, there should be 7 hoses on it. You will want to follow the ports marked T and PB and with a Power Beyond valve, run the PB line coming off of the loader valve into the Inlet of the new valve, a line from the PB port on the new valve to where the current PB line from the loader valve ends up and adding in a tee to the T (for Tank) and run the line from the Tank port on the new valve to the tee.

Then the excess high pressure flow from the Loader valve will flow through your new valve and into the selector valve (which chooses if it goes to the 3 point valve, or the backhoe valve).
Low pressure return to tank will then go to the tank hose and not have to go out through the backhoe or three point hitch valves.

Aaron Z

Thank you Scotty and Aaron. I’m going to look at it closely today and take some pictures and likely have some more questions.

 

[Smokeydog]

What you want to do can be done in several different ways.

Probably one of the easiest is to simply divert flow using a T from the front remotes. This is easily done by several methods. Keep in mind that when you put a T in an open flow hydraulic system you are creating an alternate path in a system designed to feed all the flow into a whichever path is less restrictive. So the path not used needs to be either blocked or restricted. This can be done by a manual switching valve, by a priority valve, or even by the hydraulic control valve that you use to operate the cylinder itself....but only if that control valve has a "power beyond" option and the plumbing is done properly. Return hose diameter is important for long runs.

It is important that the flow path that you choose to use must have it's own valve as well as proper return paths both from the valve and from the working cylinder.

I'm sure that something similar could be done using those attractive rear mounted quick disconnect backhoe pressure/return connections for digging and swing flow..... but I don't know which is what with those rear connectors and would be reluctant to do it myself without first studying the system and then drawing out a flow diagram showing EXACTLY what I decided to do. But there's not a reason in the world why you can't do it.

I recommended looking at the front remote first because it is a simpler single system with more than enough flow and only costs you a little more in hose length - hose which you would probably want to use anyway to get the control valve forward where it is more accessible. Remember that return hoses are generally larger diameter than pressure feed hoses

I think you would find it an advantage to get the Kubota workshop manual for you L48; & advise everyone who enjoys tractor mechanics to invest in the manufacturer's workshop manual.
I have one for our M59 and it has an excellent chapter on the hydraulic system with good illustrations. One for the L48 would probably answer all of your questions.

Another thing that will help is to learn how to read a hydraulic flow diagram in schematic form. The workshop manual has that diagram as well. If you simply sketch out your proposed hydraulic circuit in schematic fashion it is hard to go wrong.
rScotty

Teeing into the front loader 3rd valve function remotes between the valves and QDs would be quick and cheap to get a rear remote. No new valves to buy or mount. Two tees, two lines, two QDs and mounting block.

Downside is blocking by unplugging either the front or the rear depending which one you want to use.

Independent control using additional valves would rival the cost of dedicated OEM rear remotes.

The single rear remote on the B26 costs nearly as much as three for M59.

Don’t know if the L48 has front remote? Still available? Aftermarket from everything attachments?

 

[rScotty]

......Looking, the loader valve appears to be mounted on the loader tower. .....(in the M59)
Aaron Z

See how easy it is to be fooled? I don't know about the L48 but that FEL loader control valvesure fooled me on the M59.

It sure looked to me like my M59 FEL loader valve would be located in the loader valve tower by my right hand - just exactly as you say and I expected too. It would just make sense to find it there....
After all, that's where it is traditionally, directly under the control valve handle on just about every tractor in the world.

So I was surprised when I finally did find the M59 loader control valve. It's down underneat the floor of the tractor behind two steel covers and operated remotely by cables. I'll start another thread about my efforts to find and lube that M59 loader control valve so we don't get too far off subject here.
rScotty

 

[aczlan]

See how easy it is to be fooled? I don't know about the L48 but that FEL loader control valvesure fooled me on the M59.

It sure looked to me like my M59 FEL loader valve would be located in the loader valve tower by my right hand - just exactly as you say and I expected too. It would just make sense to find it there....
After all, that's where it is traditionally, directly under the control valve handle on just about every tractor in the world.

So I was surprised when I finally did find the M59 loader control valve. It's down underneat the floor of the tractor behind two steel covers and operated remotely by cables. I'll start another thread about my efforts to find and lube that M59 loader control valve so we don't get too far off subject here.
rScotty

I looked up the L48 parts diagrams before posting and they appear to show it being right under the stick, not down low like on your M59.

Aaron Z

 

[jgoodma1]

I'm going out now to start looking at it. Now......don't know if this has bearing on the idea of using the front loader valve but I do have a 3rd function hydraulic setup on the loader for a grapple or 4 in 1 bucket. I'm guessing that might be the only front remote and is now not available to use for the TNT......but I'll know shortly. Also, I was looking at post by Brian on Green Tractor Talk and he had pictures of a setup that looked like it would work for my L48 (if the loader valve won't work). Please see the attached pictures.I'm thinking I could mount the control valve on the fender like in these photos. The 4 hoses coming out of the top of the valve would go to a new manifold that would be attached to the ROPS. In the photos, the hoses that supply the valve and return to the tank are coming up from underneath the tractor somewhere. In the case of the L48, I'm suggesting that the supply and return hose would instead, plug into the 2 QA fittings on the rear of the L48 tractor, that supply the backhoe dipper tick and bucket (there is one more QA on the left side that provides for swinging the dipper stick). The backhoe valves are attached to the backhoe assembly and are downstream of those QA fittings. This would be a pretty easy setup to put together. Do you think that would work?

.

 

[aczlan]

I'm going out now to start looking at it. Now......don't know if this has bearing on the idea of using the front loader valve but I do have a 3rd function hydraulic setup on the loader for a grapple or 4 in 1 bucket. I'm guessing that might be the only front remote and is now not available to use for the TNT......but I'll know shortly. Also, I was looking at post by Brian on Green Tractor Talk and he had pictures of a setup that looked like it would work for my L48 (if the loader valve won't work). Please see the attached pictures.I'm thinking I could mount the control valve on the fender like in these photos. The 4 hoses coming out of the top of the valve would go to a new manifold that would be attached to the ROPS. In the photos, the hoses that supply the valve and return to the tank are coming up from underneath the tractor somewhere. In the case of the L48, I'm suggesting that the supply and return hose would instead, plug into the 2 QA fittings on the rear of the L48 tractor, that supply the backhoe dipper tick and bucket (there is one more QA on the left side that provides for swinging the dipper stick). The backhoe valves are attached to the backhoe assembly and are downstream of those QA fittings. This would be a pretty easy setup to put together. Do you think that would work?

View attachment 635732View attachment 635733View attachment 635734.

The problem with that is that I believe the valve which turns on the fluid out the backhoe valve turns on both the fluid for the swing as well as a fluid for the rest of the backhoe valve.
As such, you'll be flowing fluid through one while deadheading the other which is a recipe for a very short life on the pump.
You will need to verify if this is the case, if that is how it works you cannot do it that way.
The other issue would be that if it does work that way, when you have your new valve enabled, your three point hitch will be disabled, that would not be overly convenient from a usability standpoint.
If you're able to tap into one of the two lines before it reaches the selector valve that chooses if the flow goes out to the backhoe or to the 3-point.
I would follow the hoses coming off of your loader valve and see if you can tie in to the power beyond port coming off of your loader valve going back to the selector valve.

Aaron Z

 

[fried1765]

I知 going to try to put together an after-market 3PH linkage for my Kubota L48 TLB (it didn稚 come with one) and the factory linkage is over $2000. I壇 like to include a hydraulic top link and I知 wondering if I can use the quick-connect ports that normally supply the backhoe to feed the hydraulic top link cylinder after the backhoe has been removed?

I will likely never remove my L48 backhoe (except to repaint), and my tractor (2006 -used) came to me with 3 rear remotes that I will also likely never use.
A total waste....for me.

 

[aczlan]

I will likely never remove my L48 backhoe (except to repaint), and my tractor (2006 -used) came to me with 3 rear remotes that I will also likely never use.
A total waste....for me.

You could use one to run a hydraulic thumb on your backhoe.

Aaron Z