Kubota L4740 return to sump

Josh1564 · Jul 2, 2020

Hey everyone, I need some help. I am trying to run a hydraulically driven motor like a bush hog on my l4740. Now I know I can get the pressure from my rear remotes or third function but the return line needs to go to sump. I do not like the idea of running the hose into the fill port for it will cause frothing in the fluid. The only option i can seem to come up with is to cut and tee into the steel line that comes from the back of the loader valve and goes to the tank. I cant find any open ports. Any thoughts?

Leejohn · Jul 2, 2020

Maybe you could tee in at the loader valve and not cut any hard lines.

Dave M7040 · Jul 2, 2020

Look closely at your owners' manual. On my slightly larger M series, the rear remotes can deal with supply and return for a hydraulic motor.

I run my Samurai sickle mower this way.

In the attached image from my owners manual, it clearly shows one remote of a pair is pushing and the other returning to the sump.

This is not unlike a loader valve. When a cylinder is extending, the retract side of the cylinder is being routed to the sump by the loader valve.

Dave M7040

dstig1 · Jul 2, 2020

A first concern is that i doubt you have enough flow in the tractor's hydraulics to run a bush hog. I have looked into similar uses regarding a rotary broom, and was advised that there is not enough flow to do that and still drive the tractor.

jaydee325 · Jul 3, 2020

According to Tactordata, the pump on the L4740 puts out 9.8 gpm.

What is the required flow rate of the motor(s) that are desired to be operated?

Peter 315 · Jul 3, 2020

You can run it to the fill port that's how the l3800 was when they first come out with rear remote kits for it, And that's how the post pounders are set up....

Josh1564 · Jul 3, 2020

The minimum flow rate for the motor is 8 gpm
Dave, I thought I could return it through the remotes but the company advised against that.
I have attached 2 screenshots of my loader valve from the WSM

5030 · Jul 3, 2020

Most of the M series have a threaded boss tapped into the back PTO end cover just for returning fluid to the transmission case (sump if you want to call it that). Where my loader returns to on both my M's. Not sure if the smaller units have that but it's easy enough to drill and tap an access port in that location, though you would have to remove the rear cover so as not to contaminate the fluid inside.

Dave M7040 · Jul 3, 2020

Josh1564 said:
The minimum flow rate for the motor is 8 gpm
Dave, I thought I could return it through the remotes but the company advised against that.
I have attached 2 screenshots of my loader valve from the WSM
View attachment 661980 View attachment 661979

Could you post some info on the hydraulic side of your cutter. i.e. motor spec and model

Does the motor have a case drain?

You could always connect into the T line on your loader valve.

Running a high hydraulic flow though your system will start heating it up. You may find you need a cooler and fan for the return flow.

Dave M7040

jaydee325 · Jul 3, 2020

Dave M7040 said:
Running a high hydraulic flow though your system will start heating it up. You may find you need a cooler and fan for the return flow.

Dave M7040

My thoughts exactly. Having a constant 8 gpm flow through the return on a rear remote is going to have a lot of restriction through the quick coupler and any other down stream choke points. That is going to make heat and probably why the manufacturer recommended against that.

I'm thinking the rear remotes on CUTs are primarily designed for intermittent use to extend and retract cylinders.

A self contained PTO driven hydraulic power pack rated for the desired flow may be the better option.