Hst vs gearbox

[Lanadog]

Hello all, I’m new to forum and not mechanically inclined. My TG1860 seems to have HST issues, not as smooth or strong, and having spells of pulsing, like intermittently engaging and then slipping. Don’t think the hst has ever been serviced in the 20 years I’ve had it (bought used 2002). Operators manual specs show both a gearbox oil and a hst oil capacity, and says gearbox oil should be changed every 300 hrs. Question: do I have a gearbox AND the hst? And I only change the gearbox oil, not the hst oil? Manual says nothing about changing hst oil. Does hst oil ever have to be checked or changed?
Sorry for such basic questions but like I said I don’t know or do much except change the engine oil/filter and top off coolant. Any info would be appreciated.

 

[GeoHorn]

TractorData.com Kubota TG1860 tractor information

www.tractordata.com

I had to look up what you have…. You probably need a workshop manual if the operating manual doesn’t specify.

 

[lugbolt]

Hello all, I’m new to forum and not mechanically inclined. My TG1860 seems to have HST issues, not as smooth or strong, and having spells of pulsing, like intermittently engaging and then slipping. Don’t think the hst has ever been serviced in the 20 years I’ve had it (bought used 2002). Operators manual specs show both a gearbox oil and a hst oil capacity, and says gearbox oil should be changed every 300 hrs. Question: do I have a gearbox AND the hst? And I only change the gearbox oil, not the hst oil? Manual says nothing about changing hst oil. Does hst oil ever have to be checked or changed?
Sorry for such basic questions but like I said I don’t know or do much except change the engine oil/filter and top off coolant. Any info would be appreciated.

yes the gearbox and hst are separate

hst is hydrostatic transmission

gearbox is what the mowing deck uses. Shaft comes from the engine and runs back to the gearbox which has a pulley on it--which runs the mower deck.

You're concerned with the hst in this discussion, or that's the way it sounds to me based on your description.

THe hst on these is "non serviceable". SO basically you have to remove it from the tractor to service it. Don't try doing it any other way unless you're just adding oil to it.

They have a filter inside the transmission (HST) that can get dirty over time. IT is replaceable but it requires removal of the transmission from the tractor, then flip it upside down on a bench. Remove the pan, and prepare to break a few of the bolts off (common), and drill them out. I've not don a lot of them, but of the ones I've done, about 75% of them had one or more broken pan bolts. Once the pan is off, the filter stares you in the face. Pull it off (just pulls out) but HOLD the part that the filter is seated on-because if that plate comes up, there is a ball & spring underneath it that will usually fall out, and down inside the transmission. Hydrogear makes the transmission, but they don't show where the check ball & spring go, so you have to figure that part out if you drop it (and often you won't know until you reassemble to find out that the transmission doesn't work).

 

[Lanadog]

yes the gearbox and hst are separate

hst is hydrostatic transmission

gearbox is what the mowing deck uses. Shaft comes from the engine and runs back to the gearbox which has a pulley on it--which runs the mower deck.

You're concerned with the hst in this discussion, or that's the way it sounds to me based on your description.

THe hst on these is "non serviceable". SO basically you have to remove it from the tractor to service it. Don't try doing it any other way unless you're just adding oil to it.

They have a filter inside the transmission (HST) that can get dirty over time. IT is replaceable but it requires removal of the transmission from the tractor, then flip it upside down on a bench. Remove the pan, and prepare to break a few of the bolts off (common), and drill them out. I've not don a lot of them, but of the ones I've done, about 75% of them had one or more broken pan bolts. Once the pan is off, the filter stares you in the face. Pull it off (just pulls out) but HOLD the part that the filter is seated on-because if that plate comes up, there is a ball & spring underneath it that will usually fall out, and down inside the transmission. Hydrogear makes the transmission, but they don't show where the check ball & spring go, so you have to figure that part out if you drop it (and often you won't know until you reassemble to find out that the transmission doesn't work).

Thanks much for clear explanation. I’ll go ahead with the gearbox oil change knowing that it’s separate from the hydrostatic transmission I’m not qualified to work on the hst but you mentioned that you could add hst oil somehow. Does it have a dipstick and filler port like the gearbox? How do you know if it’s low on hst oil? Thanks!

 

[GreensvilleJay]

think this is what you have...
1 pix shows 'vent' where you could add correct oil...other shows the $200 HST filter kit. when HSTs get hot,oil vapours out(lost),get hotter faster, more oil 's lost,eventually they 'die' (loss of power,like going up a hill...) Easy to service, drop belt, 4 bolts,toss onto bench,drain oil ,replace filter,...

 

[TheOldHokie]

Thanks much for clear explanation. I’ll go ahead with the gearbox oil change knowing that it’s separate from the hydrostatic transmission I’m not qualified to work on the hst but you mentioned that you could add hst oil somehow. Does it have a dipstick and filler port like the gearbox? How do you know if it’s low on hst oil? Thanks!

If you have never added HST oil in 20 years I have a pretty good idea of whats wrong.

Start by finding the HST dipstick and makung sure its full. If you are lucky that will fix the slipping problem.

Dan

 

[GreensvilleJay]

I didn't see a dipstick. probably made same as JD HSTs, designed to fail.

 

[TheOldHokie]

I didn't see a dipstick. probably made same as JD HSTs, designed to fail.

Appears to have a plug for checking oil level.

Dan

 

[Lanadog]

Thanks guys. Like y’all I can’t identify a plug or vent or dipstick on the hydrostatic trans. So I’ll leave it alone for now and just make sure other maintenance stays up to date. She still mows good just slower off the block and going up a grade and having that feeling of slipping which is only at low rpm’s maneuvering in the garage.

 

[TheOldHokie]

Thanks guys. Like y’all I can’t identify a plug or vent or dipstick on the hydrostatic trans. So I’ll leave it alone for now and just make sure other maintenance stays up to date. She still mows good just slower off the block and going up a grade and having that feeling of slipping which is only at low rpm’s maneuvering in the garage.

Check the HST oil level and if needed correct it now. If the oil level is low and you continue to operate it that way you will toast the transmission and you will be lookung for a new machine.

Dan

 

[lugbolt]

just fill it to the top of the vent hole, then put the vent hose back on as I remember. Service manual outlines it.

changing the filter is easy, as long as you don't lose the check ball. Or break off half of the bolts in the pan-which is almost a guarantee. If it's just one, might get away with leaving it be. If it's more than one, have fun extracting them. 1/4-20 self tapping triangular threads as I remember. And they're about as hard as a drill bit.

 

[whitetiger]

You have an oil-level check plug in the upper rear of the right-hand axle housing.
You fill up to the level check plug by adding 20/50 conventional oil through the breather hose port on the top of the trans-axle.

 

[Nicksacco]

Here's a couple of videos that offer explanations of how the Hydro's work.

and another

 

[GreensvilleJay]

You really should fill the HST !
If you don't it WILL self destruct sooner than later, as oil vapours out,inners get hotter, more oil vapours out and then expensive parts get damaged making it 'not economical to repair'.
Best oil is a full synthetic, able to withstand heat. At the very least keep CLEANING the crud OFF the HST's cooling fins !

 

[rbargeron]

Nobody has yet mentioned that your HST's DRIVE BELT could just be worn or loose?

HST units usually hold up amazingly well (so do the newer bigger ones). On most Kubota machines the HST is driven directly by the engine but on your TG1860 it is at the back end of the tractor, driven by a belt from the gearbox.

The HST belt is separate from the mower belt. It can get worn and start slipping - which lines up with the symptoms of good grass cutting but intermittent motion. Another possibility is the tension idler pulley spring 130 (lower drawing) is weak or disconnected.

The No. 79 drive belt, (part 140 on the HST belt drawing) is Kubota part no. K1211-12120 and is widely available for about $13 delivered.

 

[rbargeron]

Hope above is useful - take care, Dick B.

 

[fried1765]

Nobody has yet mentioned that your HST's DRIVE BELT could just be worn or loose?

HST units usually hold up amazingly well (so do the newer bigger ones). On most Kubota machines the HST is driven directly by the engine but on your TG1860 it is at the back end of the tractor, driven by a belt from the gearbox.

The HST belt is separate from the mower belt. It can get worn and start slipping - which lines up with the symptoms. of intermittent motion. Another possibility is its tensioner pulley spring is weak or out of adjustment.

p.s. On these diagrams - the No. 79 drive belt, (part 140 on the HST belt drawing) is Kubota part no. K1211-12120 and is widely available for about $13 delivered.


View attachment 126634 View attachment 126635

Excellent advice!

 

[Lanadog]

Can’t thank all responders enough for advice and diagrams. Nick Sacco posted videos showing how a hst works. Fascinating! I had no idea how a hydraulic motor works. Am trying to digest all this. Thanks to Dick at rbrrgeron for the drive belt lessons. That will be my first project since I can’t find a dipstick or fill plug or vent hose on the hst. Problem is the mowing season is just starting and I hate to have her in the shop now. Could be worse I guess.