I know this is an old thread and I'm not trying to hijack it, but I am having the same problem on my 2010 850 Xp. My right front output seal is leaking. Well I drained the fluid and it was milky. The seal itself is not hard to replace. But I have a question on how the seal started to leak. I recently installed a triangle atv snorkel kit. The snorkel kit has you put bellows on the vent tubes to make it a closed system incase you would submerge it, water won't go into the differential through the vent tube. Now is that a good idea putting the bellows on the vent tube? Could to much pressure build up in the differential to cause the seal to let loose? I don't have much expierence with different types of snorkels, and was hoping for some input from other members.