The rear differential of my truck is puking gear oil from the vent, any ideas?
The most common cause is aeration of the oil. This is normally caused by contamination and results in millions of tiny bubbles causing the oil to greatly expand. I have also seen cases of a partially restricted vent causing this problem. The pressure is increased to a point where oil slung by the ring gear is blown out, rather than falling back to the lower end of the housing.
