85W-140 Gear Oil Too Thick?

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Hello,

My Dad has a Kubota 105X tractor, and I'm planning on changing the front axle case oil. The owner's manual calls for either Kubota UDT fluid or 80W-90 gear oil to be in the front axle.

I have been shopping around my local auto stores, Rural King, and TSC for a good gear lube. The better quality 80W-90 gear lubes are ranging anywhere from $9 to $14 a quart! I need eight quarts! Whew!

Rural King has Mystik 85W-140 in stock for only about $2.79 a quart. The back of the bottle makes it sound like good stuff, but I am concerned with the viscosity. Is 85W-140 gear oil too thick for an application calling for 80W-90 gear oil?

I would be grateful for any thoughts, comments, and opinions.

Thanks
 
It'll only be too thick when cold. Once the gear oil warms up, it will be OK.

Is eight quarts for the front end only? If so, sounds like its overengineered and doesn't need the 'thick gear oil bandaid'. I would shop around and try to find a 90wt.
Most synthetic 90wts around here are ~$10. I would think that the blends or mineral ones would be much cheaper. Why not find the Mystik 90wt?????
 
I believe that is what's called for in my rear diff. on my F150 so it can't be all that bad.
 
unDummy,

Yes, eight quarts for the front end only. Kubota made the front axle a seperate gear case even from the front wheels. Since the 105X tractor has bi-speed turning/optional 4-wheel drive, the front wheels have gear boxes right behind them, attached to the end of the front axle. That means there really three seperate gear boxes! All with their own drain and fill plugs!

It is quite the impressive machine. That is why I want some kind of gear lube in the axle case instead of the optional UDT transmision fluid. The UDT fluid just seems like it would be a kinda thin viscosity fluid for the axle case for such a heavy machine.

I have looked for the Mystik 90wt, but I can't find it! It is a little frustrating with the limited number of products that I can find locally. I guess the reason Rural King stocks the 140wt is because it is the most common viscosity for heavy duty applications?

Schmoe,

It's funny you mention your F150, my Dad has a 2006 Tundra, the owner's manual calls for a 140wt gear lube in the standard rear diff., however, for the limited slip diff. it calls a 90wt. gear oil. The equipment manufactor's recommendation of the fluids they would like you to use sure are a lot of fun, aren't they?
 
""Is 85W-140 gear oil too thick for an application calling for 80W-90 gear oil?""

For slow speed as in your use NO go ahead and use it it will be fine.
bruce
 
I appreciate all the replies.

bruce381, thanks for saying the 140wt is fine to use. You wrote "For slow speed as in your use ". What is the difference between slow speed or high speed using the 85W-140?
 
I use 85w140 in the front/rear diffs of my Jeep. This thicker gear oil usually comes from the factory in the rear diff of trucks/suvs that will see towing duty, so take that for what it's worth. I've had no problems with it. When cold it flows like a, well, 85w rather than a 80w. Go for it.
 
slow heavy loads will like a thicker oil if highway speeds oil churning may reduce mileage some but in general gears sets like the thickest oil you can run at the temp range you are in. I use 75/140 syn both front and rear on all my 4x4.
bruce
 
njohnson,

This probably is not what you want to hear, but. . . .
The Kubota UDT is perfect for your tractor. Or, if you don't want to stick with the house brand (maybe it's pricey), you can pick up a 5 gallon pail of something like Chevron THF 1000 for $57 here in Hawaii, probably less in Indiana. It meets Kubota's specs. Anyway you look at it, it's pretty cheap and does the job.

Cheers, Mark
 
The UDT/Super UDT are 9-10cst fluids. 80w90 gear oils are typically 14-16cst, which is already cosiderably thicker.

With winter coming, and not knowing the lubrication method in those gear boxes(splash, pumped, wings, groves, combination), I would probably NOT go to a 140wt unless it was a full synth($12-$15/quart). If your location was along the equator, I would not fear the '85w'-140wts as much.

There are several manual trannies that do NOT tolerate thicker gear oil. The gear oil flow is reduced and the gears/bearings are starved of coolant/lubricant. Why risk that with your gearboxes?

Just be glad that Kubota gives you a choice in place of the factory fill. Since 90wt gears oil are an easy find, I would just pay up and use them.
 
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