Oil & Fuel So Valvoline produces ALL of Kubota lubricants...

[5030]

Cavitation is one possible source of whine but not the only one. Port design of the rotating group components is the primary whine reducer.

Generally gear pumps are limited to 85 degrees C and piston pumps to 100 degrees C but the important parameter is fluid viscosity. Piston pump optimum range is 16 to 36 cSt - stay in this range and the rotating group should get infinite life. But outdoors it痴 impossible. A cold start at freezing is going to have a typical oil at 400 cSt.

So for normal operation the range is 10 to 400 cSt. Kubota UDT is between 9 and 10 cSt at 100 degrees C so one could consider that to be the internal oil temperature limit - but where can you measure it? Easiest is using an I-R thermometer on the filter but that is the oil going into the hydro, the coldest part of the loop. A 15W-40 synthetic is good in high temp areas like AZ because it is about 14 cSt at 100 C.

I mention synthetic because mineral oils use viscosity enhancers in a 15 base oil to get the 40 top end. Problem is the enhancers shear down in high pressure hydraulic systems leaving you with a straight 15. Quality synthetics don稚 shear down. Somewhere in my files I have a shear down spreadsheet from our testing of various oils and it痴 quite dramatic but I could never give out that info except in generalities.

The hydraulic suppliers I work with focus on viscosity being the critical factor, not temperature. Now as a retiree spending my time farming, I get obsessive measuring hydraulic oil temperatures. Part of that comes from having to resolve a problem with failing hydros in Arab Emirates. However my Minnesota farm where it rarely reaches 100F is no challenge compared to commonly exceeding 120F in the Persian Gulf. But even in America there are problems.

I had a problem with hydros on machines working at the Palm Springs airport coming to a stop because the oil viscosity was so low at 122F that it leaked past the control seals and wouldn稚 allow the pump to stroke under load. The pump supplier redesigned the seals but in the meantime our crutch fix was straight SAE 50 transmission and drive train oil (not gear lube - no-no for hydraulics.

Crazy to be out working on a runway when the airplanes can稚 land due to sinking in the asphalt but that痴 why I was paid enough to keep myself in new equipment (mostly) while my nephew, who is my farming guide, buys 40 year old tractors and has a full time and a part time mechanic to keep them limping along.

It is enjoyable to be able to closely monitor my small stable precisely rather than having one call from the Gulf and the next call from a contractor in China at 16,000 foot elevation asking if his turbo is going to spool out of control in the thin air.

Was a hard read, fixed it for you. Interesting.

 

[rScotty]

SNIP........ Kubota UDT is between 9 and 10 cSt at 100 degrees C so one could consider that to be the internal oil temperature limit - but where can you measure it? Easiest is using an I-R thermometer on the filter but that is the oil going into the hydro, the coldest part of the loop. SNIP.... .

Kubota says the high end temperature for their HST oil is between 40 to 60 degrees C.... Which is between 104 & 140F. I'd say that means keeping the fluid below 140F is going to be difficult when working in the summertime.
If I were going to use mine hard in the summer I'd certainly go for a high quality full synthetic oil. That wouldn't be a bad choice in any case.

Interestingly, John Deere - who makes and sells the very reliable JD310 loader/backhoe all over the world - has recently changed from recommending their Hy-Gard trans/hydaulic fluid to recommending that straight motor oil be used in their hydraulics. Recommendations are a minimum of 10W-30, with a 5/15W - 50 preferred. Those machines have a torque converter rather than a HST transmission, so they don't have the peculiar swash plate type sliding friction that HSTs do.

For measuring temperature there must be someone who makes a simple remote sensor that can be either inline or taped to a hydraulic hose. Anyone know of one?
Or you can do pretty much the same thing by using an old-fashioned $5.00 candy thermometer, a wad of insulation, and some tape.
rScotty

 

[Smokeydog]

Kubota says the high end temperature for their HST oil is between 40 to 60 degrees C.... Which is between 104 & 140F. I'd say that means keeping the fluid below 140F is going to be difficult when working in the summertime.
If I were going to use mine hard in the summer I'd certainly go for a high quality full synthetic oil. That wouldn't be a bad choice in any case.

Interestingly, John Deere - who makes and sells the very reliable JD310 loader/backhoe all over the world - has recently changed from recommending their Hy-Gard trans/hydaulic fluid to recommending that straight motor oil be used in their hydraulics. Recommendations are a minimum of 10W-30, with a 5/15W - 50 preferred. Those machines have a torque converter rather than a HST transmission, so they don't have the peculiar swash plate type sliding friction that HSTs do.

For measuring temperature there must be someone who makes a simple remote sensor that can be either inline or taped to a hydraulic hose. Anyone know of one?
Or you can do pretty much the same thing by using an old-fashioned $5.00 candy thermometer, a wad of insulation, and some tape.
rScotty

Knowing the hydraulic/trans temp would be valuable bit of information. Measured from a good reference point even better. Line, filter, cooler inlet, pump suction??? There might even be plugged port somewhere made for a temperature sensor? Next step if you have a reliable way to measure the HST temp, what must it be from cold startup to operation? Normal operating temp? High temp? How to interpret is the next hurdle. Started a separate post on measuring HST temperature.

 

[5030]

Kubota says the high end temperature for their HST oil is between 40 to 60 degrees C.... Which is between 104 & 140F. I'd say that means keeping the fluid below 140F is going to be difficult when working in the summertime.
If I were going to use mine hard in the summer I'd certainly go for a high quality full synthetic oil. That wouldn't be a bad choice in any case.

Interestingly, John Deere - who makes and sells the very reliable JD310 loader/backhoe all over the world - has recently changed from recommending their Hy-Gard trans/hydaulic fluid to recommending that straight motor oil be used in their hydraulics. Recommendations are a minimum of 10W-30, with a 5/15W - 50 preferred. Those machines have a torque converter rather than a HST transmission, so they don't have the peculiar swash plate type sliding friction that HSTs do.

For measuring temperature there must be someone who makes a simple remote sensor that can be either inline or taped to a hydraulic hose. Anyone know of one?
Or you can do pretty much the same thing by using an old-fashioned $5.00 candy thermometer, a wad of insulation, and some tape.
rScotty

My Kubota's both have large hydraulic oil coolers in front of the Rad. In fact, every one I've looked under the hood on has a large hydraulic oil cooler.