L3400 3-point hitch adjustment

[Chilly807]

Good news here, I think. Just got my L3800 back from my dealer with a smooth operating 3ph. Dealer and Kubota regional service rep took my valve apart yesterday and found it was not set to the appropriate suggested factory settings. I was told they made one adjustment and put it back together to find decent results. I am totally pleased with the performance of the vertical motion at extremely slow lever speed. I did notice that when curling and uncurling the FEL bucket the 3pt does lower about an inch and then goes back to original height after bucket curl. I personally don't feel this will hinder my intended use of the FEL and 3ph as I don't normally use both at the same time.

I asked my dealer what specifically was adjusted, what the original dimensions were and ultimately what it is set to now. He didn't have the numbers with him, but the Kubota rep wrote everything down. I should be provided with this data soon. Will keep you posted.

If I knew how to post a video, I would. Can someone help me with this? I have video of before and after on my iphone.

From the sounds of it, I think they adjusted the set screw to match the specs listed in the manual.
This is what I did, and the results are the same too. What happens is that both the raise and lower circuit is active in the valve even in the neutral position, to maintain a given 3ph position. That's why the lift is so smooth, it's being dynamically balanced by the oil flow in and out of the valve.

When you operate the loader, which is upstream from the 3ph, the oil flow is diverted from the 3ph to provide loader function. Once the oil pressure is removed from the "raise" side of the 3ph valve, the hitch drops until the feedback linkage closes the "lower" poppet valve and the hitch stays steady. When you stop using the loader, the oil pressure is restored to the "raise" valve and the hitch lifts again. Once this happens, the feedback linkage opens the "lower" poppet again and oil flow resumes through the valve.

Mine maintained height all night with a rear blade mounted, so it isn't like it slowly drops all the way to the ground.

I didn't like the way it moved up and down every time I used the loader for snow clearing, and I had some concerns about heat buildup and possible valve wear, although I may be worried about nothing.

The part that still bothers me is that Kubota is saying nothing about this. The valves are obviously being adjusted to a different setting when they leave the factory for a reason. If that's human error, they've been doing it consistently for several years. If it's to provide what the factory considers to be acceptable performance, I can understand that, but why is no mention made of it?

Did you hold the loader valve against the relief for a few seconds to see what the the hitch did, or only curl the bucket briefly? Mine dipped slightly whenever I moved the loader or rear remote at all, then dropped more if I held the lever long enough to activate the relief valve.

Sean

 

[Chilly807]

...was just surfing the net and ran across this statement, thought I would throw it out for any comments?

"...Unfortunately this is not any easy adjustment as the top of the HST must be removed to gain access to the valve. The valve then needs to be removed to be adjusted, (via shims or springs, not sure at this time) then placed back into the tractor then tested..."

I saw that myself a couple of days ago... it's not quite like that. They're right about the not easy part, taking the tractor apart to get at the valve is a pain in the a**. Until I took mine apart, I wasn't sure exactly what I'd find under the top cover. Once the cover's off, adjustment of the valve is easy.

If you can live with the hitch settling, setting it to the manual specs is a one step process. When you re-install, it's as good as it gets, albeit with some side effects.

Sean

 

[Chilly807]

Did someone want to look up the valve *I THINK* I got: It might be the valve from an L3010 Grand L, part # 31351-39604 but I never saw it or got any paper work to confirm this. Sorry, that's the best I can do.

Dan,

From what I've read, the number 31351-39604 refers to the valve type (Type 3), not necessarily the part number, although they may be the same for convenience. According to some manuals, that is the valve that is installed in all the newer L series tractors.

The older type valve (Type 2) is a 31391-39002, and there may be variants within that designation as well.

Clear as mud..

Sean

 

[teg]

...the number 31351-39604 refers to the valve type (Type 3), not necessarily the part number, although they may be the same for convenience. According to some manuals, that is the valve that is installed in all the newer L series tractors....Clear as mud...

Thick mud, at that... with your bit of info... I may have to look at the manual again. So you think I have the same valve as yours?

I might have to open mine up and take a look, just out of curiosity.

 

[smweatherman]

For what it is worth. 31351-39604 shows up as a valid part number on sites like Messicks and Colemanequip. It appears to be the part number for the L3010, L3710, and probably others.
Parts for Kubota L3010DT/GST/HST

From the same sites the YR908-xxxxx series also appears to be a valid part number, with YR908-00105 being the most current version of the control valve.
However, compare the blow-up from the L3010 parts diagram above to the blow-up of the YR908-00100 valve from my MX WSM, and they certainly look the same internally. I am not convinced the Grand L valve is the answer to those with the newer "type 3' valves to begin with.

I haven't had one apart though. My MX4700 (YR908-00104) is at the dealer right now addressing this same problem.

Wxman

 

[Chilly807]

Thick mud, at that... with your bit of info... I may have to look at the manual again. So you think I have the same valve as yours?

I might have to open mine up and take a look, just out of curiosity.

According to the information I have, I agree with smweatherman's post below regarding the valve in the L3010. My info shows the L4300, L3010, L2900, L3410, L3300, L3710, L3600, L4310, L4200, L4610, MX5000 having the Type 3 31351-39604 valve. I don't think the manual is up to date, because it shows the L2800, L3400, and L4400 having the Type 2 31391-39002 valve.

Since the valve works well in most of the tractors in the first list, I don't think it's an adjustment issue, rather more of a design problem with the L2800/L3400/L3200/L3800 cylinder and 3 point case. It's a small piston with not much travel, so anything less than really smooth fluid control is going to cause jerky performance. The larger tractors, like the L4400 and the MX series have larger pistons and a different top case, so the problem isn't as bad, if it exists at all.

If that's the case (no pun) then it explains why the problem continues to haunt the "economy" L series since they share the same components as the older L2800/L3400/L3700SU.

The next theory is going to take some explaining, so please be patient with me. The L series are relatively light, short tractors, compacts in the true sense of the word. If you try to lift too much weight (over 2000 lbs at the lift arm ends) you're going to be doing wheelies. Mine gets light with a 5 foot bush hog on the lift and no loader attached.

So, since Kubota uses the main relief valve to control the pressure at the 3 point valve, the full pressure of 2300 psi gets applied to the lift piston, resulting in a lift force of 2000 lbs at the lift arms (rated performance). I suspect that adding another relief valve at the 3 point would have resulted in higher costs, so the engineers responsible for this design calculated the piston size they needed to achieve that safe lift capacity, and built the tractor accordingly. Unfortunately, a side effect of the small piston diameter is sensitivity to fluid flow rates.

J252's experiment with the flow divider valve illustrates how sensitive they are, he made his quite smooth by adding the divider.

For Kubota to eliminate this, I think they'd have to go a long way back to the drawing board, install another relief valve and build a new top case with a larger piston. There may not even be enough room in the trans case to accomodate a larger top case.

Anyway, that's simply not going to happen as long as the economy L's are a good seller, and they certainly fill that requirement.

That's my conspiracy theory:laughing:

Sean

 

[LD1]

According to the information I have, I agree with smweatherman's post below regarding the valve in the L3010. My info shows the L4300, L3010, L2900, L3410, L3300, L3710, L3600, L4310, L4200, L4610, MX5000 having the Type 3 31351-39604 valve. I don't think the manual is up to date, because it shows the L2800, L3400, and L4400 having the Type 2 31391-39002 valve.

Since the valve works well in most of the tractors in the first list, I don't think it's an adjustment issue, rather more of a design problem with the L2800/L3400/L3200/L3800 cylinder and 3 point case. It's a small piston with not much travel, so anything less than really smooth fluid control is going to cause jerky performance. The larger tractors, like the L4400 and the MX series have larger pistons and a different top case, so the problem isn't as bad, if it exists at all.

If that's the case (no pun) then it explains why the problem continues to haunt the "economy" L series since they share the same components as the older L2800/L3400/L3700SU.

The next theory is going to take some explaining, so please be patient with me. The L series are relatively light, short tractors, compacts in the true sense of the word. If you try to lift too much weight (over 2000 lbs at the lift arm ends) you're going to be doing wheelies. Mine gets light with a 5 foot bush hog on the lift and no loader attached.

So, since Kubota uses the main relief valve to control the pressure at the 3 point valve, the full pressure of 2300 psi gets applied to the lift piston, resulting in a lift force of 2000 lbs at the lift arms (rated performance). I suspect that adding another relief valve at the 3 point would have resulted in higher costs, so the engineers responsible for this design calculated the piston size they needed to achieve that safe lift capacity, and built the tractor accordingly. Unfortunately, a side effect of the small piston diameter is sensitivity to fluid flow rates.

J252's experiment with the flow divider valve illustrates how sensitive they are, he made his quite smooth by adding the divider.

For Kubota to eliminate this, I think they'd have to go a long way back to the drawing board, install another relief valve and build a new top case with a larger piston. There may not even be enough room in the trans case to accomodate a larger top case.

Anyway, that's simply not going to happen as long as the economy L's are a good seller, and they certainly fill that requirement.

That's my conspiracy theory:laughing:

Sean

I agree that there is someting inherintally wrong with the 3PH design of this series.

BUT, I dont think it is due to a small piston.

Just for kicks, I measured it when appart. (as well as other geometrical points) so I could calculate the ACTUAL lift capacity of the hitch.

At any rate, the piston is a pretty sizable 2.950". ALMOST 3".

Allthough I am not sure how that compairs to things like the GL's or the 4400, but the only other 3PH I have had torn appart was the 8n. And I know its piston wasnt nearly as big. Maybe 2.5" at the most.

But if the L4400, L2900, 3010, and others that use this piston have a much larger piston, then maybe???

 

[LD1]

Just thinking out loud here, and I know it is probabally impossible.....but I would almost prefer a valve that was more like a loader valve.

Eliminate the PCV for the 3PH control.

And simply have a valve that has an up and a down. With a float in the down position, and a detent for up (like a logsplitter return) that when the lever is pulled up, the hitch raises until at the top and then kicks out.

If you want to lower it, just hold the lever until you are where you want.

If you want to raise it, hold the lever until you are where you want.

And have a float at the bottom:thumbsup:

Would that not be simpler than these complex PCV's

 

[Chilly807]

Just thinking out loud here, and I know it is probabally impossible.....but I would almost prefer a valve that was more like a loader valve.

Eliminate the PCV for the 3PH control.

And simply have a valve that has an up and a down. With a float in the down position, and a detent for up (like a logsplitter return) that when the lever is pulled up, the hitch raises until at the top and then kicks out.

If you want to lower it, just hold the lever until you are where you want.

If you want to raise it, hold the lever until you are where you want.

And have a float at the bottom:thumbsup:

Would that not be simpler than these complex PCV's

It would be simpler, no question.. the problem I see is where you want a repeatable setting, like using a bush hog, or a turning plow. The advantage of the PCV is when you put the lever in a given position, the hitch goes to the same spot every time.

Sean

 

[LD1]

It would be simpler, no question.. the problem I see is where you want a repeatable setting, like using a bush hog, or a turning plow. The advantage of the PCV is when you put the lever in a given position, the hitch goes to the same spot every time.

Sean

I knew in my head that sounded too good to be true. I forgot about the repeat-ability:thumbsup: