So on my way home from getting an O2 Sensor I started to here a grinding noise in the front end somewhere. It is not the brakes as I cant really feel it in the pedal or steering wheel. Tried putting it in 4 wheel drive and it still made the same noise. The truck shifts fine, not hard or anything so it doenst sound like a tranny issue. Wondering if it could be in the front diff? I am gonna take the cover off and check it out tomorrow. What kind of fluid do I put back into it and is there a gasket made for it or do i just use a silicone sealant? Thanks, Paul