99 Silvy transfeer case leaking??? crack?

I have a 99 silverado z71 4x4 with 114,000 miles.....I have a leak on the top of my transfer case and it is not a nick from a stome or anything hitting it, but it looks like the tranfer case housing was weak from the factory and wnt now. I can see a spider like web about the size of a dime that is leaking. I wipe it away and it comes back after a few seconds. What Do I do next? DO I get a new transfer case? Get a new housing??? or try to fix the leak somehow with something like "JB" weld....??? Is this a common proble or has anybody else heard of this?????

I'd drain the sytem, clean it up with some brake cleaner, and JB weld it. Probably leaking because the aluminum is porous.