Is my box blade too heavy for my tractor and damaging the hydraulics?

[me0418840987]

On that same note, what is the approximate capacity of the 3pt on a ford 8N. I have a little over 1600 lbs of steel I beam on mine. Makes the filled tires squat a little, but been on there for the 17 years we've had it.

 

[Verticaltrx]

I recently put a Land Pride 54inch 420lb box blade on my Kubota B1750 4wd hst tractor. The manual said the weight limit for the rear lift arms are
380lbs so I'm over by 40lbs.

That blade is not too heavy for your tractor. If you are referring to the figure in the manual that states 'max load on lower links' or something to that effect, that figure is per lift arm. So you can actually safely lift 760lbs. Kubota also lists in the 'implement limitations' section the size of box blade they intended for the tractor. Generally these are pretty conservative and my guess is the blade you have is reasonably sized for your tractor.


As for the fluid coming out, that is a bit disconcerting, but probably unrelated to the size to box blade you are using. Hopefully you can get it figured out.

 

[SSdoxie]

Just thinking out loud but what about the lowering speed control, if not set to match weight of the blade, tractor shut off with hot oil then drop the blade. Could the oil pushed somewhere it's not supposed to go?

 

[slowzuki]

No. The lowering speed control just adjusts the orifice returning to the sump from the 3 point valve.

To those talking about the 3 point causing the main relief to bypass, what are you talking about? With position control that should never happen unless the hitch is out of adjustment.

The only way to suck air into the 3 point lift cyl is to force the hitch to lift higher than its setting. I've done this lots and never sucked air but if the seals were poor it could happen.

 

[Leejohn]

"""""To those talking about the 3 point causing the main relief to bypass, what are you talking about? With position control that should never happen unless the hitch is out of adjustment."""""

Right on!!!!! If the relief is opening up, you should be doing some adjusting.

 

[deere5105]

Just about every tractor that has a 3pt system would have a 3pt relief or a pump relief, but it is most common to put the relief in the 3pt area. The tractor may or may not ever have a loader installed.

If you have a hyd gage installed in the hyd system, when you raise the 3pt to max up, the relief valve will activate and screech. Look at the gage to see the relief pressure.

If you raise the 3pt and do hear the screech, that means that the pressure is at a level set by whoever. Most relief valves are set equal to the loader valve if installed.

The relief should be about 50 to100 psi below the max pump pressure.

You need to check the relief pressure anyway to see if the hyd system is working as advertised.

Your comment about the "relief valve will activate and screech" caught my attention. I have a JD 5303 with JD 522 FEL. I have noticed that I can hear a slight humming when the 3PT is fully lifted. The noise is not very loud and continues unless I bump the lift control down. I assume this is the lift pump running. I have noticed that when operating the FEL that if I reach the end of the dump cycle and still have the control in the dump position I hear a screeching type noise. I have also encountered this before when attempting to lift a heavy object that is beyond what the loader can lift. I have been concerned about the noise I hear and again to the best of my recollection these are the only times I hear it. Is it likely that this is what the noise is, the pressure relief activating before overloading the system?

 

[J_J]

Everything you describe is related to the relief valve.

Just expect to hear that noise, as it indicate that the hyd pressure is at the pressure setting for the that relief valve. That also indicates you are working at max force as the pressure is what develops the hyd force along with the size of the cyl.

If you don't hear that noise when the cyl's are maxed out, then something is wrong.