Most clutch-type LSDs will require some sort of friction modifier to allow the clutches to work properly. You can buy this as a separate additive to add to a bottle of gear lube, or you can buy gear oil with friction modifiers already added to the formula. Check the specs of your differential to see what the manufacturer recommends. It probably sells its own formulations. Here, Moore adds Auburn's friction modifier to gear lube destined for the Monte Carlo. Our Crown Victoria was treated with the Ford limited-slip additive we bought from our local dealership.