kubota b7100 hst problem

[stubbornrichard]

well for the past 5 years i have been using my little hst kubota with one big problem. It has been losing driving or push power (it has a front end loader) especially when it gets hot, i have changed both the 2 metal tubeular screen filters and the paper hydraulic filter and same problem. i put new hydraulic fluid in to, now the problem occurs when i go to push dirt it makes this very loud whine sound and just dosent have the power. it even has a very hard time going up a small incline, i know these tractors make a little whineing because of the hydro static trans, but i think there is a big problem. so if anyone can give me some ideas as to what can be the problem i would be very thankfull. i already tried the big equipment dealers around here but they didnt know AND THEY WERE KUBOTA SERVICE STATIONS/DEALERS!!!!!!!! haha, so mabe its the trans itself or just the pump im just lost. thanks again

 

[alchemysa]

I had a similar problem in my 1550. Cleaning the wire mesh screens fixed it, but you've already addressed that. Another possible cause suggested by a kubota mechanic was air leaking into the pipe that runs from the mesh filter to the HST. So check all those fittings. And I think recently someone solved a similar problem by filling the new screw-on paper filter with oil BEFORE they screwed it on.

Are you having this problem in low range too? My 1550 is still totally gutless in hi-range but its adequate in low range.

Downloading the full parts manual free from here might help... Kubotabooks.com

(edit. Probably be better to ask this question in the Kubota Owners forum).

 

[stubbornrichard]

Thanks for the reply, yea my screens were probably flowing only 20% they were really bad, once i changed them it didnt seem to make a difference, but i will deffinately check those hydraulic tubes, dosn't seem to leak but its worth a shot, well in high range i would be lucky if it goes a few feet without stopping and whineing so its very bad but in low range once it gets hot i can make it back from the field (barely), thanks for the link, i actually bought a shop repair manual for it but the pages are not much help because the picture printing is very low quality and i can't make out what they are demonstrating.

 

[KubotainNH]

The whining sounds like a pressure relief valve opening up. I had issues with the valve on my FEL but my B6100 has gear drive.

 

[Bird]

The whining sounds like a pressure relief valve opening up. I had issues with the valve on my FEL but my B6100 has gear drive.

That was my first thought, too. I wondered whether a pressure relief valve is opening too soon; i.e., at too low a pressure, leaving inadequate pressure to push the tractor. But I don't know enough about the tractor's hydraulics to know whether that's logical or not.

 

[alchemysa]

I meant to mention that mine still screams like a banshee even though its running reasonably OK. I believe that screaming HST's are pretty normal so don't be too distressed about that. But the fact that replacing the blocked screens made almost no difference is not a good sign. If you can't find any air leaks in the suction pipe then getting the HST pressure tested is probably essential.

One other thought... could it be a slipping clutch rather than a HST problem?

 

[BotaBigot]

I agree the manuals come up short, plus I think something's lost in translation.

You've already done the basics...so, I'd concur with others here that the next thing to check is pressure relief valve/pressure test. Beyond that, it sounds internal...like wear or seal failure, which is not good news.

 

[stubbornrichard]

well im going to make an appointment with the dealer to get a pressure check unless its an easy thing to do at home ?, haha im glad that im not the only one with a less than satisfactory book i wont bother returning it. thanks guys again for all the input it's all very usefull and hopefully i can get it moving strong again because the engine runs like new and it has alot of hours on it, but im shure like most of us kubota owners know out there they run forever, the best compact tractor there is in my opinion

 

[stubbornrichard]

Oh, Well im not shure about the clutch because when it goes harder and harder into the pile of dirt it gets louder and louder and the pedal gets kind of hard to put down, but i will check that to i think there is an inspection bolt that you unscrew at the bottom of the bell housing to look at the clutch material, i am going to look at my repair manual tonite to see if i can get a better understanding on how those hydro static transmissions actually work

 

[dfkrug]

Does it behave the same way in fwd and reverse? The HST has separate
relief valves for fwd and rev, set around 5000psi. If low fluid or air bubbles
can be eliminated, then maybe it is time for a pressure test.