Hal,
Where did you get the AN-4 fitting? I'm going to do the same thing this winter when I change the gears.
I've been using Royal Purple 75W90
Synthetic in my street-driven 9" and haven't yet put the limited slip additive in (not sure what I would solve by adding it). I'm pretty happy with Royal Purple and assume any
synthetic like Mobil 1 or
Amsoil gear lube would work, as long as the requirement is for API GL-4 or GL-5. Since I have floating axles and tube seals, my capacity is just short of a gallon.
What kind of limited-slip lube is used by those that add it?
Paul