twinsticks:
Do a search for this issue, and you will find numerous posts.
I have a BX2200 with likely the same axle set-up, and had the same leak.
Before taking things apart, Kubota reccomends if you are using SUDT fluid, to change to 80-90w gear oil, and see if that stops the leak.
I believe that an "o" ring seals the lower axle pivot point, which appears to be the source of the leak.
Another case of an inexpensive part (O ring) but an semi-expensive repair due to the labor involved to change it.
Good Luck:
WALT