Broke Hydrostat twice? Why?

[crashz]

Whether opening the relief or bypassing through the open loop, the fluid is still flowing. And even though that supplied by a separate pump, its the same fluid as the HST. So if its getting hot while working, and the remote lever is accidentally activated and dead-headed for 10 hrs of hard use, that fluid will get extra hot!

But..

I'd expect that the fluid would show some degradation. Overheated ATF smells burnt. What does overheated Kubota UDT smell like?

 

[dfkrug]

I have a frame mounted backhoe. It is usually not attached. There is a lever that comes out from under the front of my seat that operates the rear remotes. The lever moves either way sideways and has a detent position at its full travel point. It is possible when entering or leaving the tractor to brush up against the lever and if you do it hard enough, it will stay at its full side detent position. I've noticed this before and I just re center the lever. There is no strange sound or any thing.

If you are causing your system relief valve (prob on the FEL valve) to be activated for extended
periods of time, then that would indeed heat up the fluid, without even driving the tractor. I do
not know if TYM uses a separate system RV for OEM AUX valves. Kioti does not, and they also
power their hoes off a detented AUX valve.

Note that SUPER-UDT is a lower-viscosity THF intended primarily for colder climates, like Idaho.
Tho I think that SUDT is a semi-synthetic THF like Kubota's UDT, lower viscosity will generally give less fluid film
protection at higher temps. Esp for the HST slippers.

I use Kubota UDT and its equivalent THF products from Chevron and Conoco. The largest Kubota dealer
in NorCal sells little SUDT, pushing all their customers toward UDT. Semi-synthetic THF products are specifically
designed to work well with HSTs and wet brakes. I do not know of a full synthetic THF (tractor-hyd-fluid).

 

[Bob Christensen]

If you are causing your system relief valve (prob on the FEL valve) to be activated for extended
periods of time, then that would indeed heat up the fluid, without even driving the tractor. I do
not know if TYM uses a separate system RV for OEM AUX valves. Kioti does not, and they also
power their hoes off a detented AUX valve.

Note that SUPER-UDT is a lower-viscosity THF intended primarily for colder climates, like Idaho.
Tho I think that SUDT is a semi-synthetic THF like Kubota's UDT, lower viscosity will generally give less fluid film
protection at higher temps. Esp for the HST slippers.

I use Kubota UDT and its equivalent THF products from Chevron and Conoco. The largest Kubota dealer
in NorCal sells little SUDT, pushing all their customers toward UDT. Semi-synthetic THF products are specifically
designed to work well with HSTs and wet brakes. I do not know of a full synthetic THF (tractor-hyd-fluid).

I did not know that the Kubota super UDT and UDT were made for colder climates. So another possible contributing cause.

For what it's worth, Amsoil tractor hydraulic oil is fully synthetic and has a higher vis than Super UDT2 and even a little higher than Chevron's tractor hydraulic oil.

But it retails for over $200 per 5 gallon bucket. But they advertise it for 'extended use'.

 

[dfkrug]

I did not know that the Kubota super UDT and UDT were made for colder
climates.

Super-UDT is for colder climates, not UDT.

 

[Coyote machine]

Bob, I think a distinct possibility is your HST's have been failing related to excessive heat over time. Though the fluid in each trans may have not shown visible or smell test issues/signs, upon lab analysis of it's condition it might well fail to pass viscosity or other testing.

Anyway, I know my Kioti dealer and I discussed the possibility of an operator being able to bump the detented rear remote lever into position without knowing it had been done and causing a no flow condition when no backhoe or other hydraulic demand was present at the rear remote. This would, and to my knowledge, HAS caused the hydro pump to fail.
The solution, remove the detent from the remote lever, OR, in my estimation, add a hose with male QDs when the hoe is not present. This is what I had made up by my dealer, and whenever the hoe comes off the hose loop goes in it's place. This also allows one to use the detented lever for items like log splitters, etc.

I would suggest this might be the easiest solution to your detented lever 'fix'.

P.S. Don't forget to add it to your checklist.:thumbsup:

We're getting there! This thread may lead to fewer HST failures for many brands - not that they're prone to failing; they're not. However, the more we all are aware of potential causes the better able we are to prevent same.

P.P.S. Amsoil is good/great product, BUT is it worth $200/ 5 gallon pail?! Who knows. I suggest that you might just scope out some other tractor brand name fluids, including Kioti's label HST. I don't know if it is synthetic a blend or just their own dino mix, but I know it too is way more expensive than TSC Traveller's universal fluid. I'm not saying it's better or worse, just pricier. I've got two 5 gal pails awaiting me changing it for the first and to date only fluid change in over 785 hours on the clock.

 

[Bob Christensen]

Bob, I think a distinct possibility is your HST's have been failing related to excessive heat over time. Though the fluid in each trans may have not shown visible or smell test issues/signs, upon lab analysis of it's condition it might well fail to pass viscosity or other testing.

Anyway, I know my Kioti dealer and I discussed the possibility of an operator being able to bump the detented rear remote lever into position without knowing it had been done and causing a no flow condition when no backhoe or other hydraulic demand was present at the rear remote. This would, and to my knowledge, HAS caused the hydro pump to fail.
The solution, remove the detent from the remote lever, OR, in my estimation, add a hose with male QDs when the hoe is not present. This is what I had made up by my dealer, and whenever the hoe comes off the hose loop goes in it's place. This also allows one to use the detented lever for items like log splitters, etc.

I would suggest this might be the easiest solution to your detented lever 'fix'.

P.S. Don't forget to add it to your checklist.:thumbsup:

We're getting there! This thread may lead to fewer HST failures for many brands - not that they're prone to failing; they're not. However, the more we all are aware of potential causes the better able we are to prevent same.

P.P.S. Amsoil is good/great product, BUT is it worth $200/ 5 gallon pail?! Who knows. I suggest that you might just scope out some other tractor brand name fluids, including Kioti's label HST. I don't know if it is synthetic a blend or just their own dino mix, but I know it too is way more expensive than TSC Traveller's universal fluid. I'm not saying it's better or worse, just pricier. I've got two 5 gal pails awaiting me changing it for the first and to date only fluid change in over 785 hours on the clock.

I agree with you. There are just too many issues uncovered in this thread that indicate high temps or low viscosity.

The good news is that inside of a week, if all goes well, we'll get to the bottom of this thanks to Dkrug, and a report will be forthcoming.

The position of the detent lever is such that it will be easy to tie it in the neutral position and release it when I have the backhoe on. I have no other hydraulic rear attachments.

Oil in future? Well, I'll await the postmortem, but I use Amsoil or Mobil 1 for all my other machines, several of which I bought decades ago and never had any oil related issues. The extended change intervals that I do use pays or almost pays for the extra cost. And my TYM only uses one pail per change.

 

[Fluid]

Hi Folks,

Haven't been on here for years now, but about 8 years ago you were super helpful in getting a tractor when I knew nothing and then keeping me alive while I learned.
I wound up with a TYM 273-27 HP CUT with all the attachments. Now 8 years and 1300 hrs old I love it.
My issue here now is that at about 400 hours the Hydrostat broke - tractor wouldn't move at all. It was replaced under full warranty and was fine again.
A few weeks ago, almost all forward motion stopped. Reverse was fine. Implements were fine.
I reversed the relief valves and still no forward.
Checked pressures:
Rear (backhoe) 1800 lbs - this is correct.
2 check valves at Hydrostat - 500 lbs each - should be 2500 lbs.
Feed pump check point - 125 lbs - correct.
I have no nearby dealer so I hauled it to Jordan in Post Falls, Idaho. Can't say enough good about these guys.
They diagnosed faulty Hydrostat. Had a low hrs. used one on the shelf! Replaced and all is again well.
My question is that since everyone says there is rarely a problem with these Hydrostats, how did I break 2 of them? and how do I keep from breaking another?
Background:
10 acres of mostly old growth forest. Path building. Lots of bucket and grapple work.
Hard work - 1300 hrs now but oil and filters always changed with the best - Mobil 1 and Kubota Super UDT transmission fluid.

I am putting this in Owning/Operating instead of the TYM section because of the lack of traffic there and I think this could have happened to any tractor.
I have always received lots of help from this site and I thank you in advance for any advice you can give me now.

Bob

8 years old with 1300 hours, two broken hydrostat units and you love it. You did not tell us how much it cost to fix it this last time, parts, labor, fuel hauling it and time. And you love it? I can not understand people sometimes. The best thing you could do for yourself is sell it now that it moves under its own power and buy a John Deere. You will be able to give the JD to your grandkids or great grandkids.

 

[Fluid]

Hi Folks,
My question is that since everyone says there is rarely a problem with these Hydrostats, how did I break 2 of them? and how do I keep from breaking another?
Bob

Two answers to your questions, answer #1 You bought a TYM. answer #2 Sell it and buy a John Deere.

8 years old 1300 hours two broken hydrostats and you love it. HOW and WHY?

 

[Bob Christensen]

Well Fluid,

The purpose of this thread is to determine how this happened.

If it turns out that the fault is inherent to the tractor, or TYM in general, then I'll have to agree with you although buying a new tractor has multiple issues for me.

But what if the damage is found to have been my fault- through ignorance or whatever? The tractor is otherwise perfect for me and with the kind of help I am finding here, I could easily change my habits. I know I can do this; I've been married 40 years.

 

[TSO]

Fluid ... You're an idiot.

Bob ...I'm sorry, but I don't think that excessive heat due to fluid quality had anything to do with your failures. Many many people use store brand fluid without failures. And, like Coyote mentioned, HST's are not prone to failing.

I'm leaning towards your detent issue, or, something else internal that's leading to the failures.