3-Point Hitch Another L3700 with Jerky lift

[Harvest Moon]

I had a close look at the feedback linkage tonight, as well as reading Harvest Moon's saga (all 20 pages) from 2009 !

About the only thing I could see that might help is to increase the length of the moment arm (lever) on the valve, which would result in slower closing as the lift arm reaches it's desired position. What that would do to the actual position of the 3ph I'm not sure without actually trying it.

Nice to see some fresh ideas! I haven't given up trying to figure this out but I must admit that I'm at a loss for a simple solution.

My latest thought is to modify the lowering speed valve (LSV). The LSV is a variable/adjustable check valve. I am pretty sure all the fluid to enter the cylinder passes through this valve. If reducing the size of the ports would reduce the flow through the valve it would reduce the excessive and sudden rush of fluid and temper the jerky response. I'm basing this theory on the fact that the L3010 uses the same position control valve as the best performing L3400's and probably the L3700 but has a larger cylinder and by all accounts does not have the jerky issue.

Unfortunately, I'm not sure how realistic this idea is and I fear that there may be some complications, like strain on relief valve or the hitch not lowering with light implements. Calculating the right port size to modify the flow, if it would even work, is somewhat beyond my current skill set.

On a positive note, with the right specifications, I suspect that a machine shop could make the modification very easily. Another plus, the LSV is easy to remove/replace.

It's really too bad Kubota did not address this with the L3700, I'm sure otherwise it's a great machine. As I noted earlier, I'd expect to see the best of the position control valves in the L3700 but with a .5 higher GPM than the L3400 the effect may be amplified.

 

[Chilly807]

I spoke with my local dealer yesterday afternoon regarding the 3 ph issue. He had heard from a few people that weren't enamored with the roughness of the
3pt. One of them said that opening the restrictor valve had helped his considerably. I'll give that a try, but it will make for some pretty quick lowering of implements which is another problem in itself.

He did say he would look into the situation with the regional sales/service reps and see what they had to say about a possible solution.

I call that a very positive approach to a customer's concerns, whether they have a "fix" or not. There was no mention of "that's just the way it works", or "this is an economy model, and that's to be expected".

He did say he's seen the video on Youtube of the post hole digger boom and the bucket of water.

I've been pretty impressed with their customer relations since I've owned the tractor, I'd recommend anyone in my area to give them a try when shopping.

I'll try to have a closer look at feedback linkages on different tractors this weekend, the valve may be part of the problem but I don't think it's the entire cause.

If one were to restrict the oil flow into the lift cylinder, that would probably help quite a bit, the trick is where to put the restriction? It has to be after the valve and before the cylinder, otherwise you can impede the flow of oil through the system (power beyond) which will result in some passing over the relief valve and heating the oil. I also think it should be an adjustable restrictor to allow for temperature differences, desired rate of rise, etc.

Has anyone tried raising the loader while also raising the 3pt? Someone mentioned that earlier in the 2009 thread, but did we ever follow up? If that works, that means that a slower flow of oil (caused in that case by another demand on the pump flow) has the desired effect. Ergo, a restrictor will work provided it doesn't cause other problems.

Sean

 

[ccsial]

He did say he would look into the situation with the regional sales/service reps and see what they had to say about a possible solution.

This is interesting to me. In 2005 When I complained, the dealer sent a tech to my home and he looked at it and said "that is not right". I got a call later from the service manager that he found something on the Kubota web site and there is a fix. They picked up my tractor and fixed it for free. I was not there to watch but they removed the seat and the whole top of the housing and changed a valve. It was much better but not perfect. I could live with it now. Before it jumped a full inch at a time.

I wonder if Kubota took this info off the web or just what happend that dealers are still in the dark. Or are the new ones working like mine is now but still not considered smooth enough by many owners.

 

[TheGoose]

Cool, we have the same tractors!! LOL.

This is interesting to me. In 2005 When I complained, the dealer sent a tech to my home and he looked at it and said "that is not right". I got a call later from the service manager that he found something on the Kubota web site and there is a fix. They picked up my tractor and fixed it for free. I was not there to watch but they removed the seat and the whole top of the housing and changed a valve. It was much better but not perfect. I could live with it now. Before it jumped a full inch at a time.

I wonder if Kubota took this info off the web or just what happend that dealers are still in the dark. Or are the new ones working like mine is now but still not considered smooth enough by many owners.

 

[TheGoose]

If anybody has a contact at Kubota I would like to send them a message and possibly a video showing how difficult the 3-pt can be when using any kind of boom pole implement. Not to mention dangerous. I was kind of told by the dealer that it was just a characteristic of the tractor but I would like to get an official Kubota response.

 

[Harvest Moon]

Sounds like some of you have honest and fair dealers that would like to and are willing to help. It's nice to hear.

If one were to restrict the oil flow into the lift cylinder, that would probably help quite a bit, the trick is where to put the restriction? It has to be after the valve and before the cylinder, otherwise you can impede the flow of oil through the system (power beyond) which will result in some passing over the relief valve and heating the oil. I also think it should be an adjustable restrictor to allow for temperature differences, desired rate of rise, etc.

The lowering speed valve is between the position control valve and the cylinder, it actually tops the cylinder. It's body is cylindrical and has a hole that passes through it (so it's actually two holes,) opening into it's hallow core. The fluid appears to flow through these openings, then through the body of the valve, passing through a check at the bottom of the valve body and straight into the 3 point lift cylinder. The top of the valve body is the adjustment knob, which sets a stop in the valve body to limit the flow while lowering the implement. All the way tight locks the check shut.

My though is, pull the LSV, it's 2 easy bolts, tap the two holes (I'd call them ports) thread plugs into them and drill a smaller holes in the plugs. If it worked, it's really easy and fairly inexpensive. But it wouldn't be adjustable by any means.

 

[InThePines]

I sent my original complaint using the customer service email option here:

https://www.kubota.com/F/secure/contact_putract.cfm?

And a Service rep contacted me a few days later.

 

[Harvest Moon]

Has anyone tried raising the loader while also raising the 3pt? Someone mentioned that earlier in the 2009 thread, but did we ever follow up? If that works, that means that a slower flow of oil (caused in that case by another demand on the pump flow) has the desired effect. Ergo, a restrictor will work provided it doesn't cause other problems.

Sean

Good question, I'm among the guilty of dropping the ball on this one. Someone has to try it, I won't have a chance for a few days, at least.

 

[InThePines]

Good question, I'm among the guilty of dropping the ball on this one. Someone has to try it, I won't have a chance for a few days, at least.

I just tried this test, raising the FEL and the 3 pt at the same time, there was no difference, approx 1400 RPM

 

[Harvest Moon]

Interesting and thanks for sharing that.

Not sure what it means. Maybe reducing the flow to the three point won't make a difference in the jerking or maybe raising the loader at the same time doesn't reduce the flow rate to the 3 point make a difference in the jerking.

Hopefully, someone out there can interpret this and maybe help determine if modifying the lowering speed valve would help. I wonder what EE Bota is up to?