thanks Soundguy, I've read alot of your posts over the last year and value your advice. The gearbox holds less than half a quart. Looks like I'll stick with a dedicated gear oil, as per the manual. I did however find this response from a Google search I did. You might find it interesting, of course I'm not sure how credible the author is.
Specified oils are as follows: for most temperature ranges use 10w-30 engine oil with the most current diesel rating (CG, CH, etc)/ for the transmission and final drives use Kubota UDT or Super UDT. Heavy gear oil, 80w90 is also approved for the rear axles instead of UDT but we always install UDT. Mower gearbox calls for straight weight SAE 90 gear oil, but over the years we have best performance with lower heat build-up using Kubota UDT in the gearboxes. This applies to front axles in Kubota tractors with front wheel assist.
My recommendation to all our customers is to stock and use only two oils for their tractors; any good name-brand diesel rated oil with viscosity according to temperature, use, and owner's manual AND either Kubota UDT or Super UDT depending on use, temperature, thickness of wallet (since Super UDT is more expensive)
One final suggestion on the subject of grease for mower spindles - spend a little more and get hi-temp grease rather than chassis grease. It will hold up much better and stay where you want it, AND don't over grease. Every three or four mowings works for us. Greasing the spindles every time you mow tends to over fill and then attract dirt, debris, etc and can lead to premature bearing failure. Even the factory sealed bearings on a T-series mower are warranted under normal intended use for the machine for 2 years.
