I have an 07' kodiak 450 that i noticed started to leak what looks like gear oil, (But is black more like burnt grease) out from wear the axle meets the rear diff. The leak seemed to stop when i wasnt riding it, but once i started riding again it would come pouring out. I've checked the oil in the rear diff a number of times and the level never seems to drop, wich seem weird to me.

Can anyone explain what the problem is?

 

Sounds like the seal is bad. It is not hard to replace. There is no grease to speak of in that area and it could only be gear oil. A Haynes manual doesn't cost much and will guide you through the job.

 

the black color u see is were the oil has gotten hot and has some mud and water in it. Theres nothing hard about changing the seal just make sure everything is clean when u go back with the new one and also change the gear oil