B7800 Frt axle case oil change

[b12]

I'm ready to do a 300 hour oil change on the front axle of my B7800.
My operator's manual states that I can use Kubota UDT or Super UDT or SAE80-SAE90 gear oil.
My dealer claims they only use SAE80-SAE90 gear oil.
Capacity is 4.7 quarts.
The liquid on the front axle dip stick is very light oil and looks allot more like UDT or Super UDT rather than SAE80-SAE90 gear oil,
so it seems logical to continue using Super UDT.
My B7800 is used mostly during the winter months for snow removal and I think the
lighter weight Super UDT would offer better lubrication than SAE80-SAE90 gear oil at lower temperatures.

I imagine other Kubota Model tractors have this same front axle oil choice and I was wonder what you folks
are using and why ?

 

[freewheel3]

You can tell by the smell, gear oil stinks. If you have a dipstick on your transmission, sniff it and see if it's the same as the front axle.
You'll get a mix of replies. Some guys use UDT or Super UDT, some guys use 80-90 gear oil. Either is fine according to Kubota but there is a train of thought that the heavier viscosity gear oil is less likely to weep past seals as time goes on.
Personally, I use 80-90 gear oil mostly because there are millions of differentials using it over the last 60+ years with no problems, but also it is less expensive and more readily available.
All the differentials in my trucks use it, and they take a lot more wear and tear hauling heavy loads down the highway at -40 to +40 degrees C than a 20HP tractor puttering around the yard a few times a year.

 

[Pau7220]

used mostly during the winter months for snow removal and I think the
lighter weight Super UDT would offer better lubrication than SAE80-SAE90 gear oil at lower temperatures.

Sounds right, but it's not. Unlike an engine where the oil has to be pumped to lubricate... the gears in the outer ends are fully submerged, and the center section is half submerged. As soon as your wheels rotate 1/2 turn, everything is fully wet and lubed. I personally use gear lube because it's thicker and will reduce leakage. Sooner or later those knuckle seals will leak. Either is fine.