HST Oil Change: Fact or Fiction?

[Henro]

Hi,

I know many of today's cars do not have the need to change automatic transmission fluid. There may not even be a dipstick to check level?

I just bought another 5 gallon pail super UDT for my Kabota tractors. I now have enough to change the HST fluid in both tractors which I will do.

But I'm wondering after the first initial HST fluid change, which I think is important, if it's really necessary to keep changing the HST fluid at the recommended Intervals.

My recollection is that the fluid that comes out of my HST looks about the same as it did when it went in new.

What do you guys think?

 

[Wagtail]

I just changed the hydraulic fluid and filter for the first time at the 400hr mark about a fortnight ago. The fluid has slightly discoloured (darker) than the 31 litres of new HyGuard I put in and there were only flecks of filings in the filter. The tractor, perceptively, works better now with the new fluid.

Ideally, I have piece of mind that there is nothing wrong or potentially wrong going on with my HST system.

To me, replacing the fluid & filter at the recommended maintenance hours will (hopefully) catch a minor problem before it gets major or catastrophic.

 

[gwdixon]

As you already know, that first change at 50 hours is extremely important.

Since a HST doesn't have contact with ignition carbon it stays pretty clean looking. However, heat and hard use will deplete the additives and protection features of the oil. Choosing to use a high quality oil, as you have done, is important.

Nowadays, Kubota is recommending extended HST oil changes with a filter change in between. Apparently, the oil is of higher quality now. But the necessity of a filter change is a concern. It sounds like Kubota recognizes that there will be gunk, filings, chips, and whatever in the fluid on down the line. A filter won't get every speck.

Personally, I change the oil whenever a filter is changed. The price of the oil can be a shock, but in a relative sense, it is cheap compared to repairs. Two of my tractors use 15 gallons each and Amsoil is used in the backhoe but it is an expense that I'm willing to pay for insurance.

The choice is up to you, of course.

 

[fatboycowen]

In many of today's cars auto transmissions may have a lifetime fill, but the oil doesn't last that long. If you own one, change the fluid and filter, regardless of the recommendations, if you want the transmission to last...

 

[ovrszd]

I put Super UDT2 in my Kubota M9540. I plan to run thru a couple pairs of filters before I consider changing the fluid again.

With that said, if your tractor has rear remotes and you use them frequently you risk contamination. Also if you borrow the neighbors equipment you certainly cross contaminated your fluid with whatever he uses.

It's my opinion that maintaining the filters is much more important than changing the fluids.

 

[varmint]

I am not pessimistic to the point of thinking Kubota (and this is probably the same for other makes) recommends their fluid and filter changes at the intervals they do for monetary gain. As was noted, it is "cheap" insurance, and tractors just seem to operated better, and quieter, with fresh Super UDT 2. Or at least, we like to think so.

 

[ray66v]

It depends greatly on how you use your tractor.

Hydraulic fluid doesn't "wear out". So, unless it's contaminated, there is no good reason to change it.

The hard work here is mostly over. My tractor is now on light duty, and only used occasionally for maintenance, and snow plowing. It does not see much dirt. And, is stored indoors.

I may change the filter at some point, but, I doubt I will ever change the fluid again.

If it sat out, was working dirt all the time, and or used a lot, that would be different.

 

[jaydee325]

Many years ago, I was a heavy equipment service technician. I had the privilege of talking to several factory service zone managers of major equipment manufacturers as well as work side by side with factory engineers who came to the shop in support of prototype machines they were doing field tests of.

That experience showed me that the factory recommendations they publish in their owners manuals is not intended to increase sales of oil and filters. It is based on many millions of hours of testing over a wide range of conditions. You can be comfortable that if you follow the recommended service intervals outlined in the owners manual that you will get many years of reliable service from your equipment.

 

[joecdeere]

Heat and wear particles from the oil bath disc brakes would be enough to make me change every time, whole lot cheaper than a new hydro!

 

[murphy1244]

Heat and wear particles from the oil bath disc brakes would be enough to make me change every time, whole lot cheaper than a new hydro!

I rarely use the brakes on my HST tractor. Just let go of the pedal or switch direction.

 

[IslandTractor]

I have to agree with those who are skeptical about the need for changing HST oil regularly. Automobile transmissions are more abused than tractor HST and the rule in autos seems to be that if the fluid smells burnt then change it. My HST oil is very clean and at 500 hours (actually 400 on the oil as I did an initial change per factory schedule) it is the equivalent of an automobile at about 12,000-20,000 miles. Nobody changes auto transmission fluid that frequently.

I'm waffling for two reasons. First is whether it is necessary. Second is that a neighbor who sold his JD backhoe gave me three pails of fresh but generic HST oil. Can't decide whether to change and if so whether to use the free oil.

 

[LD1]

If you have an old backhoe like mine, there is never a need to change the oil.....only the filter every once In Awhile. The oil is always like new....constantly having to be replenished to replace what leaks.

 

[mcfarmall]

Heat degradation, the depletion of the additive package, and contamination are the main concerns.

 

[newbury]

Trust but verify. Get a used oil analysis if you are worried.

 

[IslandTractor]

Trust but verify. Get a used oil analysis if you are worried.

I've never heard of a used oil analysis on hydraulic fluid. How does one interpret the findings? Does the analysis give limits of normal for contaminants and additives?

 

[hosspuller]

Hydrostat oil like auto transmission oil suffer wear particles, oxidation, etc. The other property not yet mentioned is viscosity loss. As the oil is churned and sheared, the molecules are broken down. The newer sealed transmissions have synthetic fills but even they are not immune to viscosity loss. It's just enough to get the unit safely out of warranty :thumbdown:

 

[newbury]

I've never heard of a used oil analysis on hydraulic fluid. How does one interpret the findings? Does the analysis give limits of normal for contaminants and additives?

Here's an explanation

 

[IslandTractor]

Here's an explanation

Thanks. Where do you get hydraulic fluid tested?

 

[newbury]

Thanks. Where do you get hydraulic fluid tested?

I'm getting mine done at Blackstone Labs, but that's just because I bought a bunch of their prepaid mail in test sample containers a while back.
There's a lot of testers out there.
Check with BITOG (Bob is the Oil Guy)

And as I posted in another thread getting the sample is easy:

I admit it might be a terrible, difficult, messy project for some.

I worked the tractor (B7610) for a while to ensure warm hydro fluid.

I turned it off and lifted the seat.

I pulled out the fill plug above the three point.

I stuck a CLEAR aquarium air tube down inside and siphoned out the required amount.

Use a clear tube so you can see it.
Get the fluid warm if not hot so it flows quicker
Wipe off around the plug before pulling it.

The messiest part was the two or three drops of fluid out of the tube after I was done. But I had a full roll of paper towels handy.

 

[fatboycowen]

Blackstone is good. I also heard somewhere that caterpillar dealers can send them out for you.