So I bought 92 cruiser from guy who had the front diff. Rebuilt from a dealer for 1100$ now 1 1/2 years and 12000 miles later I went to change diff fluid and the stuff is black. Looks like grease is in it. The breather valve seemed to work. Doesn't click or anything. Do u guys think it is OK to keep running that way if I change fluid often. Or do I need to get seals redone. I need to replace front brakes soon would that be a good time to do it. I'm decent on engine but this kind of stuff is out of my element. Any info would be helpful. I use this as adventure car.skiing rafting dirt roads to backpacking. No major off reading. Thanks