I just changed the rear differential fluid in my 2007 Expedition. From what I can tell the 2007s and newer do NOT have limited slip differentials, they have traction control. When the truck is jacked up and I spin a tire one way, the opposite tire spins the other way. Per the manual, the friction modifier is only needed on models with the limited slip. This is a bit confusing since it's not offered I don't know why they put that in the manual... but my question is am I right about this that I don't need the friction modifier?