I guess I'm just seeing different, I still see the boss and the small circular indentation in the end of it. I see nothing missing. It just looks like it's been beat on a bit, but that could be the photo light and the corrosion under the paint that is causing that. I tried to get a better photo of mine, but my Top Block is in the way, well that and I got tired of kneeling down there.
I've highlighted in green the boss and circle area (if I wasn't so lazy I'm sure I could look in the service manual and see exactly what that is, then I thought let MOB do it... ) and in red the area that I thought might be welded (Heliarced?/TIG) but could be just corrosion and flaking paint. I'm starting to lose interest.
Anyway here are the photos:
well, it is the bevel gear housing; and the gasket behind it is 11061-0310 GASKET,FR GEAR CASE
but we have seen a few 'weeping" things with coolant, and droplets of "green" liquids have made there way there, because of gravity. Mostly seen on the retaining bolts tho.. but that corrosion is evident of some seapage behind, and attacking the finished paint on the housing... hmmm.. it ain't oil.. only coolant would do that.
so, a thousand mile away over the net, I'm thinking for you to look at hose connections, and bolts, all being a sealed within on the cooling system, and mitigating a leak that ends up at that point below. Where it sits, in the mating surfaces, and working under the paint corroding the finish...
do a bit more exploration, especially aroud the water pump.. loose hose clamp, or if service was done prior to the pump, anything related to it could reveal the source...
oh, and if you have an active warranty, or an extended one... make Kaw "fix" it .. meaning they provide you with a re-built output case, NEW of course, and not just blowing you off and saying 'wee''ll paint it"....
wow, when I was trying to post this/... it combined like three clipboard responses.. sorry..