Glad you found a definite cause for the leaking. Best I have been able to determine, that with how hot the differential gets, the differential gear oil expands enough to be the same as adding an additional 2 ozs., which is expanding about 9%. This is a lot, so all of that additional pressure has got to go somewhere to be released.
I have been doing a little testing on the heat generated by the differential and am about to decide that most of the heat is not generated by the differential itself but by the inner CV joints and then transferred to the differential. Am going to do a lot more testing while in Utah the next couple of weeks, comparing to other Wolverines. I just recently made an aluminum heat shield that I mounted to stop all heat from the exhaust pipe/muffler getting to the differential and from testing around the yard the differential stays cool and the inner CV joints get close to the point of being to hot to keep your hand on (especially the right side). This is with only 45 minutes of riding around at 7-10 mph in the yard so I know all day trail riding they are going to get much hotter and then the CV joints will have time to transfer the heat to the differential. As I mentioned, I still want to do some more testing, to be absolutely sure the differential is getting hot due to heat transfer from the inner CV joints but as of right now this is looking like the case.
I'm not sure the heat shield is really going to help any because I checked the temperature of the differential and inner CV joints from riding around the yard before I installed the heat shield and the diff. stayed cool and the inner CV joints got hot, the same as with the heat shield added. I added the heat shield because it was just to easy to make and install while I had the bed off for replacing all the seals in my differential.