Is it better to use gear oil or trans fluid in front axle of FWA Kubotas?

[sixdogs]

I know this has been discussed before but I'm looking for sort-of a one word answer on whether it's better to use 80W90 gear oil or transaxle fluid in the front axle of Kubotas with front when drive. Which one? Kubota says you can use either.

They come from the factory with trans fluid yet most people I know seem to switch to gear oil on the presumed belief it offers greater protection during abuse and also is it less likely to leak. Suppose there's any basis for this or if it's true?

 

[bumperm]

I'm not an engineer, but agree with the gear oil crowd. The synthetic HST trans oil Kubota now specs is good stuff, with price to match. It's designed for tight tolerances and being synthetic, lasts a long time, however it has relatively low viscosity. Generally speaking, the higher the viscosity the higher the film strength, both against metal to metal wear and shock loading. Synthetic gear oil with it's higher viscosity, seems to me, offers both higher film strength and more protection against high pressure metal to metal gear wear typically foundl in differentials, gears, and stuff like that

bumper

 

[k0ua]

The Kioti forum is full of the same questions. The manufacture also spec's either fluid for the front axle. It is filled with hydraulic fluid from the factory. I put one of the approved hydraulic fluids back in it. Mobilfluid 424. If the manufacturer spec's either, I think either will work.

 

[sixdogs]

bumperm--that's what I was thinking...that "the higher film strength and metal to metal wear and shock loading" is far better with the gear oil. The thicker viscosity is probably less likely to leak or seep out as well.

 

[bullbreaker]

I run 80/90 gear oil in mine. Also use the same for PHD gear box and BH gear box.

 

[rbargeron]

Not a one-word answer, but my dad, a gearing engineer, designed the tools used to manufacture gears, including gears used in differentials. He said that the appropriate oil for meshing gears depends in part on how the gears are made. Differential gears are spiral bevel type, with more sliding contact than straight spur-type gears. If a gear is precision cut with multiple hardening and finishing operations, then lighter-viscosity oil will give adequate "float" to prevent most metal-to-metal contact. A heavier oil like 80W90 maintains more film thickness, allowing gears of slightly lower finishing specification to still give satisfactory life in service. Kub's manufacturing standards are pretty high - which may explain why either oil is ok with them for the front axle.

 

[Baby Grand]

Whenever given the option, I try to use a gear oil with EP for anything with crossed axis gears, especially if they're spiral bevel, zerol or hypoid gears. These gears have higher sliding velocities, as rbargeron mentioned. The EP additives in these oils helps to prevent metal to metal contact and wear under high pressure, high sliding velocity conditions. Since the operator's manual says I can use gear oil in the front axle, I do.

I think the manufacturers use the hydraulic fluid because it meets the requirements and they avoid the risk of "which oil goes where" mix ups at the factory and service facilities. One less lubricant to keep in inventory also reduces costs.

Since the front seals on our smaller tractors are frequently victims of seal wear and leakage, the higher viscosity gear oil has the additional benefit of staying in the housing when a thinner oil would tend to weep out.

 

[RickB]

The Kioti forum is full of the same questions. The manufacture also spec's either fluid for the front axle. It is filled with hydraulic fluid from the factory. I put one of the approved hydraulic fluids back in it. Mobilfluid 424. If the manufacturer spec's either, I think either will work.

Exactly. For the record I use and recommend a proper UTF over gearlube when UTF is a factory recommendation.

 

[KiotiKowboy]

I went with the gear oil in the front axle of my Kioti DK50 - per the dealer's preference. I like the idea of a heavier oil for the axles - but what the heck do I know?

 

[itsjustme]

Let me tell you what my Granddad said when I was a teenager, got my first car and asked what kind of oil to use.

" Doesn't matter long as there's sumethin' in it and its kept clean an full "

That's a pretty true statement that's worked well for me over the last 45 years.