An OEM LSD gearbox's internals are no different to a NON-LSD gearbox. The OEM LSD gearbox has an open diff exactly the same as a NON-LSD box. The only difference is the casing which bolts on the side of the box. This casing contains some cogs which must work in the same way as an aftermarket LSD. Maybe someone could explain further home this works? Gearbox without the external casing on. External casing Together