which port do I use on this Kubota TnT

[driley]

I have a Kubota L5450 that I bought used. It has a Kubota TNT unit attached to the back with a cylinder on the top link and a cylinder on each lift arm. There is an additional set of QD couplers that I use to run a cylinder on my grader blade.

There are three hoses that run from the tnt unit to a block on the left side of the tractor near the rearend just under the seat. The block has three ports one labeled "P" which runs to a port on the tnt. One labeled "R" that runs to the "OUT" on the side opposite the "P" port on the tnt. The last port is labeled "T" and it runs to a port on the same side as the "P" port on the tnt.

I'd like to tap into the hydraulics to add a backhoe to the tractor. Which of these lines would I split. The mechanic at the dealer said to find the power beyond port on the tnt and add a set of QDs, one male and the other female. The when the BH is attached these connectors feed the hoe. When the BH is not attached, these connectors mate to each other to allow power to flow to the 3pt valve. Here's a couple of pics of the tnt unit.

Thanks for your help.

 

[J_J]

If the valve has a PB port, use that as stated for the BH. If not, I would remove say the left cyl hose on of the 3pt lift and use that as a supply for the BH. You will have to bungee the lever to open for the cyl hose that you removed .

If you remove the BH, just reconnect the hose back to the 3pt left lift cyl.

 

[J_J]

driley, you said:


[ There is an additional set of QD couplers that I use to run a cylinder on my grader blade. ]


Why not use the grader blade QD's outlets for the BH. It should be controlled by a valve, or switch if electric. If the lever is spring to center, you will have to bungee the lever open to feed the BH.

What ever you do , the valves have to be in series for open center system.

 

[driley]

If the valve has a PB port, use that as stated for the BH. cyl.

Yeah, I'm assuming that one of the three would be considered the PB port but I'm not sure which one it would be. My guess is that it's the OUT port on the valve that connects to the "R" port on the tractor.

What I'm thinking is that the "P" port on the tractor stands for Power , "T" stands for Tank and that "R" stands for Return. Would this be correct?

If so does it make sense then that the Return would be used as the PB port?


If I can't figure this out there's also another block on the right side of the transmission that has a hard line up to the pump and another hard line that runs back to the rear end. It has two ports that are currently plugged and a valve in the middle with one position marked "O" and the other marked "C". The manual says that I can connect an open center value inline. Here's a picture of that valve:



Thanks,

Dale

 

[J_J]

Yes, you can connect another valve inline/series.

The picture of the valve with the switch is very similar to the one I have on my B9200. That is where I picked up the flow for the 3pt log splitter. You could use those ports , but would add another 15 ft of hose and a set of QD. and when not using the BH, the two hoses plug together.

This is how I believe it works. In the normal position, the flow from the pump is sent through this valve back to the 3pt. If using the valve for a rear setup, the flow is diverted through these outlets/hoses , to the attachment on the back, and return to this valve, and then to the 3pt.

Always make sure the additional valve or the two hoses are connected.

The PB ports are normally marked as PB ,PByond

Do you have a FEL?

The hex cap on that valve is probably a relief valve.

 

[driley]

....

The PB ports are normally marked as PB ,PByond

Do you have a FEL?

The hex cap on that valve is probably a relief valve.

I don't have a loader on this tractor.

That's the thing, The ports are not marked on the tnt valve stack other than the OUT on the left side. There are two ports on the right side that are plugged and labeled IN and OUT (see the photo in my first post) but it doesn't make sense for those to be a feed since they are plugged. They couldn't be an "open center" feed since they aren't "open" right now. Unless there's something inside of that right side plate that provides the feed through, but I don't think so. On the other hand, I really don't know that much about hydraulic valves...

I suppose I could start pulling things apart and sort of reverse engineer it but I hate to do that since it's been together for at least 15 years and sometimes, once you brake a seal you have to replace a bunch of o-rings and (hard to find) gaskets.

Thanks,

Dale

 

[J_J]

The valve in the last picture you posted, will feed the BH first if selected and hoses attached and ran to the back.

There are probably several ways to do this, but it will be up to you as far as convenience.

I don't have a FEL on my Kubota either, so I ran the hoses to the back with QD's plugged together when no attachment is being used.

With the engine running, pump flow is running through this hose at all times with the selector in the 2 o'clock position.

 

[Farmerford]

The out port on the left side of the tnt valve (opposite the P port on the tnt) is probably power beyond because it is connected to the R (return) port on the block under the seat. The block under the seat probably receives the flow from the pump after flowing through the valve in your last picture on the right side of the transmission; doesn't the hard line going up from the valve on the transmission connect with the block under the seat? To test this, start the tractor and let it run at moderate engine speed with no hydraulic valves shifted; all flow into the tnt valve block will exit through the power beyond port. Therefore, the power beyond hose will heat up at about the same rate as the pressure in hose, while the tank hose from the tnt block will heat up very slowly if at all since no fluid will exit through it when no valve is shifted.

So you could break the tnt connections at the out port on the left side of the tnt block, and insert quick disconnects for the backhoe, but that seems to me the hard way to do it; you already have quick disconnects on the third spool in the tnt valve block which you use for your grader blade. Just connect the backhoe to them and tie the valve handle open when using the backhoe. The only possible disadvantage is that you lose a little (very little) pressure from directing the hydraulic fluid through the spool in the tnt valve block.

 

[driley]

The out port on the left side of the tnt valve (opposite the P port on the tnt) is probably power beyond because it is connected to the R (return) port on the block under the seat. The block under the seat probably receives the flow from the pump after flowing through the valve in your last picture on the right side of the transmission; doesn't the hard line going up from the valve on the transmission connect with the block under the seat? To test this, start the tractor and let it run at moderate engine speed with no hydraulic valves shifted; all flow into the tnt valve block will exit through the power beyond port. Therefore, the power beyond hose will heat up at about the same rate as the pressure in hose, while the tank hose from the tnt block will heat up very slowly if at all since no fluid will exit through it when no valve is shifted.

the first picture shows the hard line going into the 3pt controls.
you can see where the block bolts on in the second pic.

the 3rd is the block on the side of the rear end.

...you already have quick disconnects on the third spool in the tnt valve block which you use for your grader blade. Just connect the backhoe to them and tie the valve handle open when using the backhoe. The only possible disadvantage is that you lose a little (very little) pressure from directing the hydraulic fluid through the spool in the tnt valve block.

Yeah, I was wondering if that would work. It would be the simplest. will it hurt the valve to have it tied in one direction for a long time? It has a spring return to center.

It seems like there would still be enough flow since the tractor makes around 11gpm and the BH only needs about 5gpm.

Thanks,

Dale

 

[J_J]

If the valve is rated for 11 GPM's, then it will pass 11 GPM's.