Kubota L3400 rear hydraulics and 3rd function mods

[ch47dpilot]

Got most of my 3rd function and rear hydraulics plumbed and working. Only need to make brackets for the Quick Disconnects. I used as much of the original plumbing to reduce cost. The original PWR Beyond hose from FEL became the PB for the new valve and a new hose runs from the FEL to new rear hydraulic valve. I don't have a grapple so not sure how the floor switch will work. Total cost was about $400, most purchased through Surplus center. They do have a smaller selector vale that would have worked for $100 less.



I do have a question. Currently the power beyond puts the priority at the FEL, then the rear hydraulic then the 3PT. When I max out a cylinder which relief valve is working? The one set to the lowest pressure or the one on the control valve in use. I believe my tractor is around 2200PSI but the new valve is set from factory at 2000PSI. I assume since its down stream from the FEL it won't affect the FEL but since its before the 3PT will that be affected?

 

[npalen]

I can't answer your question on which relief valve takes precedence but you might experiment with a pressure gage.

 

[BukitCase]

In an open center system, any relief valve downstream from the valve that's being actuated, will NOT come into play. Any relief valve(s) UPSTREAM in the flow path, WILL come into play... Steve

 

[old and tired]

L3400, Max PSI is 2347 (according to the manual) I'm not 100% sure about the pressure question, do you have a link to the spool?

Not sure if the relief would only activate while you are using the valve.... or if the relief pressure is also applied to the Power Beyond line? If it's applied to the PB, then it would effect the whole system, since it would reduce (and heat the oil) sending all pressure above 2000 through the relief valve back to the tank.

 

[BukitCase]

In a typical open center system, when it's in standby (all valves in neutral position) there is minimal pressure ANYWHERE in the system, EXCEPT for any stored pressure in an individual WORK port (which might be holding a cylinder from retracting, etc) - When you operate ANY control valve in the system, the flow gets diverted to that valve's "customer", IOW cylinder, motor, or?

At that time, pressure in that part of the circuit will increase til it either gets the job done, or the cylinder reaches end of travel (or the motor gets stalled) OR an UPSTREAM (nearer the pump) relief is tripped, sending the overpressure fluid back to tank (thereby limiting the pressure to the setting of the relief valve)

During the above conditions, there is essentially no fluid allowed past the valve being actuated, UNLESS that valve's being only PARTIALLY activated (feathered) - In THAT scenario, the portion of pump flow that gets PAST the valve, whether PB or not, STILL has no "work" to do; it just continues on thru the REST of the (open center) system and flows back to tank.

When making any changes to the hydraulic system, the single most important thing to make sure of ($450 experience talking here) is that you do NOT add anything to the system ahead of the FIRST relief valve after the pump...

This is why, in typical loader valves the FIRST part of the combo is the main relief valve... Steve

There's no point in having any reliefs BEYOND the first one set any HIGHER than the first one, because unless the first one fails CLOSED the rest of the plumbing will NEVER get higher than that FIRST relief. Only exception I can think of is if there's a load on something like a 3ph pallet fork (or the loader, for that matter), and the operator hits a bump - then the pressure between the valve and its cylinder (IOW, the WORK port) COULD spike - that type of scenario would probably be a good application for a secondary relief...

 

[bullbreaker]

https://www.tractorbynet.com/forums...-up-lift-capacity-l3400.html?highlight=cowboy

 

[BukitCase]

Bullbreaker, I just read thru that entire thread (365 posts) - did you have a particular point to make? If so, can you narrow it down a bit? Thanks... Steve

Edit - nevermind, 90% of the thread's about the L3400 - I don't have one, my info's more generic. Still valid for most open center tractors tho, 'cause it works :=)

 

[Peter 315]

Bullbreaker, I just read thru that entire thread (365 posts) - did you have a particular point to make? If so, can you narrow it down a bit? Thanks... Steve

HAHA.............

 

[BukitCase]

Imagine how pissed I'dve been if I'd actually had somethin' to DO :laughing:

 

[bullbreaker]

Bullbreaker, I just read thru that entire thread (365 posts) - did you have a particular point to make? If so, can you narrow it down a bit? Thanks... Steve

Edit - nevermind, 90% of the thread's about the L3400 - I don't have one, my info's more generic. Still valid for most open center tractors tho, 'cause it works :=)

I posted that because thread title says Bota L3400 , and even though i myself cant help you with your other questions I sent you that so in case you didnt know how to check and bump up your psi flow .
The guys here at that time helped me do it to mine and increased my loader cap . I dont own mine anymore but I use to call my L3400 DT(direct transmission) meaning gear shift not hydro "the mouse that roared" ! ................