Another HST noise thread.....

[General Lee]

I did some searching on the boards, couldn't find anything. Lately the HST on my B3200 has been making a "hissing" sound when the tranny is under strain. It does it in medium gear going up hills and high gear in general. If I'm driving on a flat surface and the terrain changes slightly uphill the "hissing" becomes evident. I don't know what else to call the sound other than a "hiss". Its not the typical HST whine, this hissing in addition to the wine.
Now this has been going on before my 50 hour service and after filter changes and cleaning the strainer, it is still doing it. I don't remember the hiss being evident until around the 35-40 hour mark. Almost sounds as if the pump is trying to pump fluid and its restricted. Fluid level is fine BTW.

Normal HST sound or could be an issue??

 

[Einar Kr]

I am in the same situation with my M125X which I believe is making more sounds than it should....but this has been going on since new. I have heard of problems in the M9085 (r what there number is) and that problem was because the main line, the feed to the pump was not big enough so the pump was starving.
But that problem was also from day one....so if it only appeared 35-40 hour mark
then I would look at filters and fluid. The fluid looses itｴs lubrication ability over time, and also the quality of the fluid being used has a lot to say about noise from the tractor.

 

[DiezNutz]

Lately the HST on my B3200 has been making a "hissing" sound...

Does it only happen around the used B7100 you bought? Maybe it's defending its territory.

First I've seen/heard of this issue.

 

[TalonDancer]

I did some searching on the boards, couldn't find anything. Lately the HST on my B3200 has been making a "hissing" sound when the tranny is under strain....

Does this only happen when the HST fluid is hot?

FWIW my L3240 HST will start 'hissing' under load after it has been run hard in very high temps (e.g. after using the back hoe for several hours at 1,500 RPM and 100F ). The next morning, when cooled off, it sounds normal again.

Talon Dancer

 

[General Lee]

I am in the same situation with my M125X which I believe is making more sounds than it should....but this has been going on since new. I have heard of problems in the M9085 (r what there number is) and that problem was because the main line, the feed to the pump was not big enough so the pump was starving.
But that problem was also from day one....so if it only appeared 35-40 hour mark
then I would look at filters and fluid. The fluid looses itｴs lubrication ability over time, and also the quality of the fluid being used has a lot to say about noise from the tractor.

New filters were just put on two weeks ago. Tractor has only been used 2.5 hours since then. About 1/2 of the fluid capacity was replaced during the filter change due to fluid loss changing out the filters.

 

[General Lee]

Does this only happen when the HST fluid is hot?

I wouldn't say "hot". Yesterday I pulled the tractor out to pull out my other tractor from the mud and the 3200 only basically ran for 7 or 8 minutes before pulling the tractor out. While coming back up the hill it was making the noise.

 

[DiezNutz]

Check that the parking brake is off?

 

[BeezFun]

I had a strange noise that sounded like air hissing shortly after I started my engine. I thought it sounded like high velocity fluid going through the filter. It turned out to be some kind of vibration. I discovered that if I press really hard on the left side of the hood I can make it stop, so there's something in there vibrating at a really high frequency that sounds like air escaping, or at least that's what it sounds like over the noise of the engine. Maybe it's one of the springs that helps prop open the hood going into some kind of resonance.

Have you tried putting on hearing protectors when it makes the noise? Sometimes cutting out some of the machine's background noise can make things sound different and make them easier to identify.

 

[Thomas]

Maybe rad. cap area etc.?? sounds can travel when traveling.

 

[General Lee]

BeezFun- I'll have tp pay more attention to where it may be coming from. I swear it sounds like the HST pump is starving to get fluid out. I'm only hearing it driving up hills or if the terrain changes from smooth to incline. Its like when the pump is trying to pump out more juice to keep the tractor going through the terrain, it hisses.

 

[Verticaltrx]

BeezFun- I'll have tp pay more attention to where it may be coming from. I swear it sounds like the HST pump is starving to get fluid out. I'm only hearing it driving up hills or if the terrain changes from smooth to incline. Its like when the pump is trying to pump out more juice to keep the tractor going through the terrain, it hisses.

It might be the relief valve opening on the HST. If that is the case it could be that either it's not properly working, or you are using too high of a range when going up hills. I know that my B3200 won't go up moderate hills in high range, and if I push too hard on the pedal in that situation it will open the relief valve and basically stop forward movement. The only time I have experienced that in middle range is when pushing too hard with the loader, never been able to stall the HST in low range. I haven't paid close attention to the sound it makes when this happens, but I think it might be similar to the hissing sound you described. If that's the case and you're not using to high of range for the situation, you might need to look at the relief valve. I can look in my service manual later if you needs details on what to check.

 

[General Lee]

It might be the relief valve opening on the HST. If that is the case it could be that either it's not properly working, or you are using too high of a range when going up hills. I know that my B3200 won't go up moderate hills in high range, and if I push too hard on the pedal in that situation it will open the relief valve and basically stop forward movement. The only time I have experienced that in middle range is when pushing too hard with the loader, never been able to stall the HST in low range. I haven't paid close attention to the sound it makes when this happens, but I think it might be similar to the hissing sound you described. If that's the case and you're not using to high of range for the situation, you might need to look at the relief valve. I can look in my service manual later if you needs details on what to check.

Yea, when you get a chance let me know what I need to do and where the relief valve is located. Thanks a million

 

[David_Kb7uns]

I wouldn't say "hot". Yesterday I pulled the tractor out to pull out my other tractor from the mud and the 3200 only basically ran for 7 or 8 minutes before pulling the tractor out. While coming back up the hill it was making the noise.

Have to ask, but were the correct Kubota filters and UDT or SUDT used in the change, otherwise may be a problem there.

David Kb7uns

 

[General Lee]

Have to ask, but were the correct Kubota filters and UDT or SUDT used in the change, otherwise may be a problem there.

David Kb7uns

I can only assume they were the right filters. I got Kubota filters from the dealer and they fit. Also used Kubota SUDT. The noise started before I did the filter changes though.

 

[General Lee]

I went out this evening to take a closer look at things. Fluid level seemed a little low. Just above the first notch on the dipstick. Manual states anywhere within the first and second notch is *acceptable*. I added about a quart of fluid to bring it up to the top notch. The noise doesn't seem to be as loud now but its still there especially in high gear. I don't know, may just the normal operation of the pump and I haven't noticed it before recently??
As one poster stated, it may be a vibration. So I listened closely and it does sound like it could be, only its evident when the transmission surges at the demand of fluid. For instance when pushing the forward peddle or going up inclines and the tractor is calling for more fluid.

 

[DiezNutz]

I've only experienced my HST relief valve a couple of times, and it's more of a squealing/whistling sound... not really a hiss. Unless that sounds right to you, it's probably something else.

 

[Verticaltrx]

I looked in the manual about the relief valve and in order to test it you have to have a special 5,000 psi gauge and the fittings to plumb it in to the tractor. Basically there are three ports on the bottom of the HST: P1, P2, P3 and you test one for the forward relief valve and one for the rearward relief valve. If you have the means to do it I can give you more specific details, but it sounds like this may not be your problem.