I checked the oil on my rear diff and it was a fudge like liquid. There was also a little bit of metal on the drain plug. I had a ride planned on saturday and discovered this on friday. So I tore my wifes diff out of her 550 and put it in my 850 for saturday. I got around to splitting the case today and realized that one of the case bolts was broken off and you could see where the gasket seal failed and let all the muddy water in. What I was wondering was if anybody has heard of the bolts shearing off or was this just a fluke. I just don't want this to be a common problem.