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Still have jerk in hydro

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Duane Pearl
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2000-11-13          21476

I posted a message a week or so ago about a "jerk" or a "surge" in the hydrostatic transmission of my Kubota B7500 HST. I took the tractor up to my dealer, who up to this point as been very good to me. At first they thought it was because the tranny was a little low on oil, which was their fault for not filling it up when I bought it. But that wasn't the case anyways. Even after filling it up, the tranny still wasn't smooth. They then got a little reluctant to even try and figure out what was wrong with it. They told me that whatever was causing the problem could probably only be fixed by tearing the whole transaxle apart, and that the problem probably wasn't really hurting anything. They told me to wait until I get 50 hours on the tractor, change all my fluids, and then see if the problem still persists. I thought that was kind of a cheap way out myself, but I went along with it for now. I sure would like it to work properly, as I spent alot of my hard earned money on this tractor, and money is something I do not posess in excess amounts. Let me describe the "jerk" once more, and see if anyone knows wnat it could be. As you press the pedal down, either to go forward or backward, the tractor will beging to just creep, when all of a sudden it lunges forward and the pedal gets stiff and kind of pushes back at my foot. If you continue to press the pedal down, it seems to operate smoothly. It's almost as if whatever valve the pedal is opening is not opening smoothly. It does this regardless of engine rpm, but only in high range. I wonder if it's doing it in low range, but is not noticeable because of the drastic gear reduction. If anyone could help, I would be greatful. Maybe if I could help my dealer figure out what is wrong, they would fix it for me. thanks.

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Gerald Pritchett
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2000-11-13          21480

Duane,
My B2910 acted just as you describe. It bothered me too.
I got about the same story from my dealer as you did. Not to
stop there I called the regional Kubota rep. I was told that
what you feel is the anti-creep valve closing. It will open and
close going down hill too. Any time the pressure drops below it's
setting. After you play with it a while you can feel it close
every time the hydro has to work a little harder. In low range
I could not feel it at all, middle range a little, high range
all the time. I drove a new B7500, it did the same thing.
I was also told that it could be adjusted, but it would be more
prone to creep at a stop. It worked OK so I didn't pursue it any
further.
After the 50 hr. service it worked the same, no change.
This must be something new that has been added, no one with the
older Bs have complained about it, that I have heard of.
I may not have be told the whole story about the valve,seems like
it had more torque before the valve closed. maybe a way to get the
tractor rolling easier. I don't think it's a problem, it's just the
way they work. ....

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Bird Senter
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2000-11-13          21482

Duane & Gerald, I'm no mechanic, but I've had a 1995 B7100 and now have a 1999 B2710 and I've never felt any such "jerk" and just can't believe it's normal. I don't believe I could tolerate that. ....

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Duane Pearl
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2000-11-14          21508

Gerald, I was wondering if the adjustment you speak of is in the valve itself, or in the linkage. I got an e-mail from someone talking about adjusting the linkage so that you don't notice this jerky feeling. From what I can see, this is not a problem that only I am having. There are others who are experiencing this same jerk. Is there a design flaw in the valving system? Or a manufacturing problem that is putting out bad or mal-adjusted valves? Or are they jusdt supposed to be that way. I know for a fact that when I test drove a B2410 that I did not feel any such jerk... it was just as smooth as could be. I expected the same from a B7500, and I am hesitant to believe that "that's just the way they are." I realize that it probably won't hurt anything, but I did spend alot of money for this tractor, and I sure would like to be certain that everything is ok. I sent some email regarding the situation to Kubota Corp., but no reply as of yet. I don't want to push the issue with my dealer, they have been good to me, so I am trying to become as informed as I can before I confront them again. ....

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KlayW in MI
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2000-11-14          21511

Hey DP, is the "surge" most noticable after a stop then a range change? I too have felt this "jerk" on my B2710. I mostly notice it when going from forward to reverse or visy versa after I change ranges in the transmission and mostly from high to low range just after starting to move. The difficult part is that in 30 hours of use I have felt it about only 5 times! I would describe it like this; from a dead stop selecting the range then I start moving sllooooowww, traveling about 2 to 5 inches the trans will jerk to a slightly differant (just noticable) speed with no change in the pedal. I have never felt the jerk when accelerating quickly. Sound like anything you felt? ....

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Gerald Pritchett
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2000-11-14          21514

Duane,
I did not discuss what valve could be adjusted, but I think I would let Kubota
or a Kubota dealer decide what needs to be done to your tractor. Like I said
we may not know all it does. For instance, the cruise worked real good,it
maintained the set cruise speed better than my L3010HST, and I could feel the
valve open and close going up and down hills in medium range cutting grass.
Bleeding some of the pressure may have fixed other problems, never heard
of a B with the "power steering loss" problem and the "jerk" problem.
I'm just thinking out loud on this subject. Don't take anything I say to
the bank. I'm just a tinker that likes tractors. If your not satisfied with
your tractor, drive a L3010HST, it has the "Feather step" HST, a different
machine than the HSD.




....

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Art White
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2000-11-15          21519

I've been watching this post and with interest, Take the tractor to the shop and tell them to fix it or give you a tractor that doesn't have the "jerk". It could be a safety issue if not resolved. There are not two identical mechanical things ever built but a jerk in the drive line is unacceptable to me as a Kubota dealer and I would get to the bottom of it. Often times you may have a little different noise from a machine do to the gear lash which is nearly impossible to find and we have to pass on being able to find it but a jerk in the drive train is not right. The life of the parts involved very well will have no difference in life but to adjust or replace that valve is just the proper way to fix it. A thought on the low oil. Had a customer who was getting ready to hook up his new tractor to his plow, had to change hydraulic ends on it and when he put it in the coupler he left it there but got side tracked and had to do something else. Son fresh of the school bus see's dads new tractor sitting there running hops up on goes for ride out back and of coarse playing with the levers finds by moving one lever it will squirt oil 30 feet out the back! Wow was it fun while son gets the tractor back to the plow but dad can't raise the plow due to lack of oil! What a call from this guy, he was hot and I couldn't blame him I was to, 45 minutes later my mechanic is at the farm and can't figure out where 20 gallons of transmission fluid went when the little boy shows up and talks about the oil gun on dads new tractor. It just isn't always the dealers fault! ....

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Roger L.
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2000-11-15          21523

Art, thanks for writing that piece of advice. It is particularly valuable coming from your perspective. When I started reading this thread the thing that stuck in my mind was Duane saying:
"Maybe if I could help my dealer figure out what is wrong, they would fix it for me. thanks."
After I read that sentence I suddenly felt tired and defeated by all the dealers out there who just don't care. Maybe is is because of my own experiences as an old time mechanic and repair shop owner. Your common sense answer makes my day! :-)
....

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Duane Pearl
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2000-11-15          21526

Art... I am sorry if I offended you with the "it was the dealer's fault" line. You are right in saying that it's not always thier fault. Even if it wasn't filled up from the dealership I should have taken the responsibility, and had enough common sense to check the oil level myself. Sincerest apologies on that. Now to the matter. I must say that during the purchase of my new kubota, that my dealer was just simply great, and I am not sure that they are anything less than that now. I perhaps am just a little too easy going. I don't like confrontation, and I like getting along with people. I am afraid of pissing them off, and then finding myself in perhaps an urgent set of circumstances where they just blow me off. If you think this problem with my tractor is big enough to get a little pushy, then I will just have my wife call them. :) I sure would like to hear back from Kubota on this... I am not even sure that I sent my email to the right place. Can someone post the correct email address for me? Also, the jerk is indeed noticeable in low range, but only when there is a load on the tractor. (ie pulling a box scraper) ....

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Duane Pearl
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2000-11-15          21528

Do you guys think I should give my dealer the benefit of the doubt and wait until I get 50 hrs on the tractor and change all the fluids? I seriously doubt the problem will be solved by the changing of all the fluids, and if I wait intil 50 hours I will be waiting quite a while. I just won't use the tractor that much this winter unless it snows like crazy. Also, I was wondering what kind of safety concern you are talking about Art. I mean, the jerk isn't enough to knock me off the tractor or anything, just enough to irritate me and make me ask questions. ....

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Duane Pearl
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2000-11-15          21530

KlayW in MI, I guess I really have not aswered your question yet, so here goes. The jerk does not depend on range changes... it is there all the time. When I am in high range, I feel the jerk every time I press the pedal... every single time. I did end up finding out that the jerk exists in both low and high range, it's just not noticeable in low range unless you are pulling something. What you describe, however, seems to be the same feeling that I am getting. As I press the pedal, the tractor begins to move slowwwwww, when it suddenly jerks to a higher speed... there is a difference here between you and I however... at the point where the tractor jerks, the pedal pushes up against my foot a little. And where your tractor never does this when accellerating quickly, mine does it allways but perhaps it is slightly less pronounced when accelerating quickly. I got an email from steve carver today that explained someting about the valving in these transmissions. He talks of an "ever so slight -- but noticeable feel" of the transmission going from creeping mode to pulling or traveling mode. This is not an ever so slight jerk I am feeling. It's a very pronounced jerk. I will try and post his email to me... not sure if I can. ....

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Duane Pearl
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2000-11-15          21531

This is Steve Carver's email describing somewhat how these things work, I think what he is talking about is what I am feeling. But I would say that the transition between the crawling and pulling modes is not happening how it's supposed to in my tractor. what do you guys think?

sc - I have noticed an "ever so slight, but noticeable -- 'feel" of the
trans. LOCKING IN as the tractors move from a "inching or creeping mode" to
and actual PULLING or TRAVELING mode. I am not sure that I am speaking about
the same sensation that you are.
This feature is important a not "a problem." The design gives the operator
the ability NOT to have jerky or "fighting the pedal" issues that most other
hydrostatic brands have a low speed operation. The feature that allows the
Kubota to have "more sensitive control, low noise, less pedal feedback
action" at low rpms, and then at the higher RPMs give the operator a positive
"locked in" transmission mode that delivers more power, less noise, less heat
built up -- all add to longer life.

If the words "surge, lung, jerk, leap" are simply describing a "shifting
trans function similar to the way a car feels when it is "shifting up though
the ground speeds modes as you increase speeds" then you probably are not
"quote" having a problem ... You are just feeling the transmission "do what
is was designed and made to do".
....

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Art White
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2000-11-16          21548

Daune I drove one of our tractors yesterday just to see if I could feel what you say is happening. I did feel the petal change as to the load of just moving faster. I didn't feel a jerk or what I would call a real surge. I might have alarmed some people of the safty issue. If you were to be inching close to something and you had some one on the ground working to say loading the bucket next to the garage as a potential pinch point and the tractor surged ahead, that could be dangerous. I like people to much to let that type of thing go by. I will be trying more to help you resolve this. Kubota for us as a dealer has been one of the best built units out of the box. These are my toys and my customers are part of my boys and I want the best for them. ....

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Art White
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2000-11-16          21559

Duane there is a fix to your tractor that doesn't take to long to fix it. As much as we have not had the problem I guess others have. Your problem as explained to me should be more prevelent when the tractor and tempurature is cold. The fix doesn't mean the tractor needs to be split or anything like that. If you would have your dealer call Kubota they do have a quick way to fix it. If you lived in my back yard I'd be more than glad to fix it for you. ....

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Duane Pearl
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2000-11-16          21561

Thanks so much, Art, for taking the time to help me out. I will get a hold of my dealer tomorrow and see what they can do for me. They are really nice people, who I am sure will get this fixed for me as soon as they can figure out exactly how to do it. At the time that I took the tractor up there, they had not yet heard back from Kubota, so the best they could do was tell me to wait until my 50hrs service. I don't blame them for that. Maybe Kubota has gotten back to them by now. I will keep you informed as to how things turn out. ....

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weimguy
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2017-10-07          197171

I would be very interested to know what the fix is for a jerky hydro static transmission is. I think Art said it was an easy fix without splitting the tractor. I have a Kubota B2650 just under 2 years old that has a jumpy transmission since new. When you want to creep very slowly up to something close like a dump trailer or change attachments it will all of the sudden lurch forward. This is with a steady foot, no additional movement of the pedal. It will do it every time in high range, a little less in medium range and barely notice it in low range. It's still doing it in low range, you just don't feel it as much due to the gearing masking it. It's still under warranty (barely) and the dealer says it's normal and Kubota technical support says there is no fix. It's normal. I didn't talk to Kubota tech support, my dealer did so I don't know the words they all were using. All I know this thing is maddening. I pull up to my brand new powder coated trailer trying to inch closer in medium range and it surges and bangs into the trailer. It always happens at the worst time. I hate this thing. The dealers only suggestion at this point is I have to downshift to low range anytime I want ti inch close to something. I'm sure this will be real handy when I'm doing a lot of loader work into a trailer. I might as well have a manual transmission. So if anyone has some information to fix this thing I would love to hear it. Otherwise I'll be in the market for a new tractor. ....

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Art White
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2017-10-09          197176


First thing I like to know is what is your foot position on the petal? ....

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weimguy
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2017-10-09          197177

Not sure what your referring to as far as foot position goes. Is it where my foot is on the pedal, or how much pressure I am applying? To describe it the way I think your asking, I am applying constant and even pressure to the pedal with zero movement. Since this thing is a problem, I am very conscious about my foot and the pedal. You can move the pedal ever so slightly to just inch along and hold the pedal in that exact spot. You'll then be creeping along and the tractor will all of the sudden jump or surge forward just like you stepped harder on the pedal all of the sudden. ....

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weimguy
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2017-10-09          197178

Just to add to my last post, when I took the tractor in to my dealer to address this issue I was able to show them exactly what it's doing. It's very repeatable. During their troubleshooting they grabbed a brand new B2650 off the lot and it does the same thing as my tractor does. They have no idea why. I don't have any confidence that they have a technician there that fully understands the inner workings of this particular hydro static transmission so they just rely on what someone at Kubota told them over the phone. I'm guessing that the tech support person at Kubota just looks at a database in their computer for any results. That person may not have any idea how this thing works. Kind of like when you call a companies tech support line and it's in India. They just read from a computer screen and no help beyond that. All I ever get is tech support says it's normal and my dealer says I'll have to shift to low range if I don't want it to surge. This would be like if you bought a brand new pick up truck and when you parked it in the garage and needed to creep up close the the freezer or work bench it would surge and crash into stuff. Then have the dealer say everything is okay and you just have to pull in into low gear to avoid tagging the freezer. This is either a bad design or so far no one knows what they're doing and how to adjust it. ....

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kthompson
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2017-10-17          197191

Just wondering does it do it all the time regardless if in 4 wheel drive or 2 wheel drive? I have a B2710 and think it does it a little in 4 wheel drive when on hard surfaces if memory is correct. I think it is the 4 wheel driving binding due to being on hard surface.

Art is the pro and I have the upmost respect for him and do agree with his concern for the tractor jumping into building or even pinning a person when helping hook or unhook from tractor. ....

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weimguy
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2017-12-09          197317

UPDATE:

Just got my Kubota B2650 back from my dealer here in Lynden Washington and they were able to change out some springs on a couple valves in the transmission and it now drives smooth as glass. No more jerking or jumping. It's so much better! ....

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Art White
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2017-12-13          197324


Good to hear of your success! When dealers look at problems there are many things that enter into the equation! There are times it might be the operator and there are times it is the equipment!!!! ....

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