Backhoe hydraulic connection advice

[ayak]

My recollection is that the OEM single rear remote has a separate tank return directly into the rear differential directly through the case where it mounts. There's a plate that comes off and the valve body mounts there.

(but someone will come along and tell me that I'm wrong...)

You’re exactly right about that plate location—but the bh77 gets flow into it from the ‘PB’ in the part in the pic called the ‘RR Outlet Block’ (using a 37” hose) and the flow coming from the bh77 goes into the part shown as ‘hydraulic block’ at its PB port.

 

[Russell King]

I have an L3902 and BH77 with rear remotes and trying to figure this out as well. This description makes sense, but which hose on the BH77 goes to the rear remote PB port and which one goes on the hose just removed from the rear remote PB port?

The backhoe valve should have one port that is P (power in) that would be connected to the rear remote Power beyond port. Then the T port is the outlet of the BH and connects to the tractor Power beyond port.

On the Backhoe use one male and one female coupler half and then the tractor side would be matched to the backhoe so it is easier to connect the backhoe next time (no choice how to do it).

 

[TheOldHokie]

My recollection is that the OEM single rear remote has a separate tank return directly into the rear differential directly through the case where it mounts. There's a plate that comes off and the valve body mounts there.

(but someone will come along and tell me that I'm wrong...)

The rear remote valve stack has a tank return via the mounting plate on the transmission housing.

The rear remotes get pressure from the PB port on the LOADER valve and the PB port on the valve stack returns pressure to the implement return port on the FRONT hydraulic outlet block.

When a BH77 is installed the PB hose on the remotes is disconnected from the FRONT hydraulic putlet block and rerouted to the rear to supply power to the BH77. A new return hose is routed from the rear to the FRONT hydraulic outlet block.

Dan

 

[Survivor]

The rear remote valve stack has a tank return via the mounting plate on the transmission housing.

The rear remotes get pressure from the PB port on the LOADER valve and the PB port on the valve stack returns pressure to the implement return port on the FRONT hydraulic outlet block.

When a BH77 is installed the PB hose on the remotes is disconnected from the FRONT hydraulic putlet block and rerouted to the rear to supply power to the BH77. A new return hose is routed from the rear to the FRONT hydraulic outlet block.

Dan

That's exactly how my kit from TractorInnovations is set up. It re-uses an existing factory hose and adds an extension, and adds a new hose for the new PB hose from the loader valve. There's neat clamp-on mounting kit with a lot of room for variation, plus the short hoses and break-away connectors and brackets to mount them to the ROPs.

I'm sure that I could put all this together with off the shelf parts for a little less money, along with maybe ten trips to town to get fittings with the right threads and the right length hoses and then fabricate mounting brackets for everything, But I put it all together in a half day while being really fussy about it, and then got back to work.

 

[TheOldHokie]

That's exactly how my kit from TractorInnovations is set up. It re-uses an existing factory hose and adds an extension, and adds a new hose for the new PB hose from the loader valve. There's neat clamp-on mounting kit with a lot of room for variation, plus the short hoses and break-away connectors and brackets to mount them to the ROPs.

I'm sure that I could put all this together with off the shelf parts for a little less money, along with maybe ten trips to town to get fittings with the right threads and the right length hoses and then fabricate mounting brackets for everything, But I put it all together in a half day while being really fussy about it, and then got back to work.

No, your remote valve is missing the power beyond portion of OEM plumbimg and the tank circuit is being miss-used as a pressure circuit.

You should fix that. It requires another hose going to tank. the power beyond sleeve for your valve, and some fittings for the tank return

Dan

 

[carld]

When a BH77 is installed the PB hose on the remotes is disconnected from the FRONT hydraulic putlet block and rerouted to the rear to supply power to the BH77. A new return hose is routed from the rear to the FRONT hydraulic outlet block.

Dan

I have option A and Option B shown in the image below? I *think* I'm confused about the flow of fluid in the PB port.

 

[carld]

Another question. Lot's of videos identify this as the Power Beyond port. Is this really a P and not a PB port?

I'm trying to make sure I understand your image here.

 

[TheOldHokie]

Another question. Lot's of videos identify this as the Power Beyond port. Is this really a P and not a PB port? View attachment 156668

I'm trying to make sure I understand your image here. View attachment 156669

Power beyond is a horribly misunderstood and missused term. P and PB are really the same thing.

Lets start with the L01/L02 hydraulic outlet block. The upper right port is pump pressure out to auxiliary vslves. The upper right port is pump pressure return from the last auxiliary valve in the chain and it supplies punp pressure to the internal 3pt valve. The bottom port is a low pressure tank return straight to the sump.

The red lines in my diagram designate the order and direction of the neutral circuit flow. Its common to call that power beyond. So PB from an upstream valve is P to the next valve in the neutral circuit chain. This leads to lots of confusion.

The blue lines are low pressure (close to 0 PSI) return paths straight to tank. That path is used to return oil to tank when a valve is shifted and the neutral circuit is blocked. Its also used to return oil to tank when a relief valve opens.

Dan

 

[TheOldHokie]

I have option A and Option B shown in the image below? I *think* I'm confused about the flow of fluid in the PB port.

View attachment 156666 View attachment 156667

Your PB confusion is very common. See my previous post.

Dan

 

[carld]

[QUOTE="TheOldHokie, post: 796940, member: 46622"

Lets start with the L01/L02 hydraulic outlet block. The upper right port is pump pressure out to auxiliary vslves. The upper right port is pump pressure return from the last auxiliary valve in the chain and it supplies punp pressure to the internal 3pt valve. The bottom port is a low pressure tank return straight to the sump.

[/QUOTE]

Did you mean:

The upper right port is pump pressure out to auxiliary vslves. The upper right LEFT port is pump pressure return from the last auxiliary valve ...

 

[TheOldHokie]

[QUOTE="TheOldHokie, post: 796940, member: 46622"

Lets start with the L01/L02 hydraulic outlet block. The upper right port is pump pressure out to auxiliary vslves. The upper right port is pump pressure return from the last auxiliary valve in the chain and it supplies punp pressure to the internal 3pt valve. The bottom port is a low pressure tank return straight to the sump.

Did you mean:

The upper right port is pump pressure out to auxiliary vslves. The upper right LEFT port is pump pressure return from the last auxiliary valve ...
[/QUOTE]
Yes - getting sloppy.

If I understand correctly you have factory remote and want to add a Summit monoblock to the circuit:

1. Install power beyond sleeve in the N port of Summit valve.
2. Connect power beyond on factory remotes to P port on Summit valve.
3. Connect power beyond sleeve in Summot valve to upper LEFT port on the outlet block.
4. Connect a new hose to one of the two tank ports on the Summit valve and tee it into the tank port on the tractor outlet block.

EZ-PZ

Dan

 

[Russell King]

@TheOldHokie
Please refer to the diagram above in post #27 (which I think you had posted somewhere else?)

The question I have is on the need for a PB sleeve in the rear remote and the FEL valve but not in the BH valve or the 3RD function. Basically explain (again) what the PB sleeve does inside the valve and why it is needed in some cases but not in the backhoe valve. I have not found an explanation on why that is OK and am curious about that.

Thank you in advance for your reply.

 

[TheOldHokie]

@TheOldHokie
Please refer to the diagram above in post #27 (which I think you had posted somewhere else?)

The question I have is on the need for a PB sleeve in the rear remote and the FEL valve but not in the BH valve or the 3RD function. Basically explain (again) what the PB sleeve does inside the valve and why it is needed in some cases but not in the backhoe valve. I have not found an explanation on why that is OK and am curious about that.

Thank you in advance for your reply.

Good question - here is a short but incomplete answer.

In a vanilla valve there are two low pressure tank cores inside the valve which share the same outlet port as the high pressure center (neutral) core. The two tank cores run along the outer walls of the valve and the spools go through both of them. Since thats a low pressure region the external seals on the spools are designed for low pressure operation - somthing in the neighborhood of 500-700 PSI max. Thats fine when the outlet port is going to tank but not when its being used to supply high pressure to another valve.

When the valve is being used for high pressure carry over (aka PB) a sleeve is commonly installed in the outlet section. The sleeve isolates the two tank cores from the center core and you have two outlet ports. One is low pressure return to tank (T) and the other us high pressure carry over (PB) to another valve. There are a number of reasons you want do that but first and foremost is protecting any low pressure seals in the tank cores. If you use the tank port to supply 2500 PSI oil to a downstream valve you risk blowing out the low pressure seals on the spools.

The tank ports on the solenoid operated industrial type valves commonly used for third functions are rated for much higher pressures - typically 3000 PSI or more. So the tank port can double as a high pressure carry over port without risking damage to tbe valve.

Clear as mud?

Dan

PS> The reason (most) Kubota backhoes do not need a power beyond port is because when they are mounted the 3pt is disabled. The backhoe is always the LAST external valve in the external loop and the 3pt valve is always in neutral and open to tank. Thats really a poor design. If the operator screws up and raises the 3pt lever or the return coupler fails the tank return gets blocked, tank port pressure shoots up to 2500 PSI, and the BH valve develops expensive leaks....

 

[Russell King]

@TheOldHokie

Thank you for the explanation! It makes sense and my understanding is clearer now!

I was neglecting (unaware) that the three point valve was disabled when using the backhoe. (I knew the three point system was not used but didn’t understand the valve should not be operational.). So that was the nugget of information that cleared up the confusion in my mind.

I appreciate the education!

How was your milkshake?

 

[TheOldHokie]

@TheOldHokie

Thank you for the explanation! It makes sense and my understanding is clearer now!

I was neglecting (unaware) that the three point valve was disabled when using the backhoe. (I knew the three point system was not used but didn’t understand the valve should not be operational.). So that was the nugget of information that cleared up the confusion in my mind. I

I appreciate the education!

How was your milkshake?

You are welcome - it was a good questiom.

The Doc said no milk shake until day 7.
Today is day 6

Dan