More Kubota Confusion

[284 International]

I don't think the chart selects one temperature for one lubricant and a different one for another. Instead it compares the viscosity at those different temperatures. Here is another, better chart: VISCOSITY INDEX CHART


I have attached the technical data sheets from Shell oil for gear oil and motor oil. (Available here: http://www.epc.shell.com/Docs/GPCDOC_X_cbe_24855_key_140003385862_200912032235.pdf and here:http://www.epc.shell.com/Docs/GPCDOC_X_cbe_24855_key_140002065182_97F5.pdf)

If you look at them, they take data for SM grade 10W-40 motor oil at 40 and 100 degrees Celsius, and do the same for 80W-90 GL-5 gear oil. At 40 degrees C the gear oil is significantly more viscous, but once things get to 100 degrees C the gear oil is only six hundredths of a centiStoke more viscous than the motor oil. 20W-50 motor oil is thicker than 80W-90 gear oil at both temperatures measured.

I am not an expert and don't claim to be, but the data speak for themselves. At operating temperatures, the viscosity of 10W-40 motor oil and 80W-90 gear oil are very, very close.

 

[Don87]

I don't think the chart selects one temperature for one lubricant and a different one for another. Instead it compares the viscosity at those different temperatures. Here is another, better chart: VISCOSITY INDEX CHART


I have attached the technical data sheets from Shell oil for gear oil and motor oil. (Available here: http://www.epc.shell.com/Docs/GPCDOC_X_cbe_24855_key_140003385862_200912032235.pdf and here:http://www.epc.shell.com/Docs/GPCDOC_X_cbe_24855_key_140002065182_97F5.pdf)

If you look at them, they take data for SM grade 10W-40 motor oil at 40 and 100 degrees Celsius, and do the same for 80W-90 GL-5 gear oil. At 40 degrees C the gear oil is significantly more viscous, but once things get to 100 degrees C the gear oil is only six hundredths of a centiStoke more viscous than the motor oil. 20W-50 motor oil is thicker than 80W-90 gear oil at both temperatures measured.

I am not an expert and don't claim to be, but the data speak for themselves. At operating temperatures, the viscosity of 10W-40 motor oil and 80W-90 gear oil are very, very close.

I've always been told that the thicker oil will stick on the gears longer after extended shut-down periods. And since the most damage occurs on initial usage of the machine, the thicker oil was "supposedly" better for the gears.

I'll ignore the charts, because from personal experience.............80W-90 will still be on the gears, long after 10W-40 has dripped off. I've dissasembled more truck transmissions, and rear-ends..........and car engines..............

EDIT: My observations are with older oils.......13 years or more.

Newer oils may have better adherence characteristics

 

[284 International]

I wouldn't use motor oil instead of gear oil even though the viscosities at some temperature or another are alike. Gear oil is designed for gears, motor oil is designed for motors, cooking oil is designed for cooking. I'm not a tribologist, but the oil companies have many people who are. They engineer lubricants for all those different applications, and they aren't the same product.

In short, I agree with you that gear oil will work better in its intended applications than motor oil would, and vice-versa. I had tried to just address the relative viscosity aspect of 80W-90 gear oil and 10W-40 motor oil. But I don't know why you would ignore the charts; all they do is compare viscosities. You still, I think, ought to choose something for the intended application. I think we would agree on that part: You likely don't run 80W-90 in your car's engine.

 

[sw03]

I wouldn't use motor oil instead of gear oil even though the viscosities at some temperature or another are alike. Gear oil is designed for gears, motor oil is designed for motors, cooking oil is designed for cooking..

I agree and most make this out harder then it is...Viscosities aside, the add pkg in gear fluid will protect 100X better then an engine oil in that app.

It is like my BX24 front diff, I drained the front diff (with SUDT0 at 25 hours and it was gray! I have Amsoils best gear fluid and after 200 hours, looks like the day it went in!

My old Bx22 did the same thing.

 

[Volfandt]

Keep in mind gents that the rear differential, brakes and ALL assorted assemblies within the HST of the HST equipped tractors are lubed by either UDT, SUDT or whatever equivalent one desides to replace the factory fill with. Theres no 80/90w or any other thicker lube that can be used in them, nata. Seriously, if UDT/SUDT can properly lube, cool and protect the much heavier duty rears in all their HST tractors wouldn't one expect that it would work fine in the front differential?
IMHO the prudent reasons to change over to a thicker front axle lube would be to slow a leaking seal or save some $$$'s on the scheduled maintenance requirement. What I find unusual that Kubota would even suggest an alternative to their branded product.....

re. syn vs dyno. Syn has superior qualities but then again, dyno has been keeping my 50+ yr old tractors running fine, over their entire lifespans, doing things regularly what tractors are designed to do
OF course it's JMHO
Carry on

 

[jdjdjd]

Thanks everyone for all of your answers. This is more information than I got from my dealer.
There have been some good points made here. For now I will be putting in the UDT since that is what I have purchased and the Kubota manual says it is OK. I may decide to go to gear oil next change.

 

[284 International]

Volfandt, I suspect we agree on things. I just wanted to observe that I don't think it's a good idea to say that it's ok to use UDT/SUDT in the rear end of a semi-truck, or the gearbox of my motocross bike since it works in the rear end of a large tractor. It may work, it may not. I think that if the manual says to use something, use what is recommended.

Like I was told in first grade, "Read the directions, then follow them." It seems like if an application calls for any of a variety of things, use what is easy, convenient and logical. If you buy UDT by the drum, and can run that in the differential according to the manual, run that instead of gear oil. But it seems unwise to use something in an application where it isn't allowed. Gear oil and motor oil may have nearly identical viscosities, but their additive packages are much different because of their intended purposes.

Many farm machines are running 50, 60, or 70 years after they were first sold. I really doubt these machines saw oil changes every 100 or 200 hours. I also don't think that it's very smart to copy that previous experience, either. Compared the overall cost of acquiring and operating the machine, the price of a couple extra oil changes here or there seems, to me, negligible.

jdjdjd: I think, for what it's worth, that you're doing well. Keep clean fluids as recommended by the manual in your machine. Go use it. :thumbsup:

 

[Volfandt]

284 International, I also suspect that we agree on things, more so than not
I do agree that the manual thats specific to the machine should be the basis for it's maintenance requirements. My earliest lessons learned in the maintenance trade was RTM (cleaned up for our general viewing audience )

I do not know if you own a Kubota w/the late model 4wd front axles but they do pressurize during normal operation. I don't know to what extent in numbers but I do know that if you crack the dipstick loose a few minutes after the tractor has been operated for a couple hrs of mowing you best have eye protection. The pressure I witnessed is akin to what an overheated automobile radiator produces when one inadventantly loosens the cap and fluid sprays everywhere. It could be that UDT/SUDT performs better in this type of environment than a thicker lube would. UDT/SUDT does have a high flash & boiling point.
I do know that most gearboxes and rears on autos/motorcycles are direct vented
so they may not produce the type of internal pressure I personally witnessed on the front axle of my BX23.
This produces 2 trains of though re. the Kubota 4wd front axle IMHO.
Why is it not direct vented and how does it eventually vent while it still is able to maintain it's sealing capability and not leak?
I've got over 500 hrs on my unit and it doesn't leak (yet) and hasn't required any fill.

Would a thicker lube work as well?
To partially answer this question most dealers do recommend to go to the thicker lube if/when the seals start to weep. Most that have gone this route have posted that the leaks lessoned.

So, yet another question begs asked and that is, would mod'ing in a direct vent also stem the leaking seals and/or improve the axles performance?
There have been a few that have added direct vents to these BX axles but I don't recall any long time results posted. On the surface it would appear to be benefitial but if so why hasn't Kubota incorporated direct venting if it is an improvement?

Just some more food for thought.
Dave

 

[big bubba]

somewhat a tangent here but along the lines of the thread: what about "limited slip" ft ends such as on my 8540. in the real world of vehicles, manu. recommend a gear lube with an added package for limited slip. but no mention of that from Kubota dealership or central htqts. my feeling is that the rpm is so slow it's not an issue, so i just use the straight GL5 80/90. something to obsess for the gear heads....

 

[Gary51]

When I am working across a mild slope for several minutes, I am more comfortable having the thicker, stickier oil on that uphill side gear then being worried about thinner oil all being on the downhill side so I use gear oil. I believe it will probably protect the uphill side a little longer.