You only have to add it if your vehicle came with a limited slip differential. Don’t remember if you vehicle has it look inside the glove box on the big white sticker on the back of it. If you don’t see limited slip differential printed on the back than you don’t have it. If you don’t have it you don’t need to add it. It is also a good place to look to see what gear ratio you are running. As for the additive, go to any stealership to get it, it comes in a bottle the size like 2 cycle engine oil mix does. I used Mobil 1 75/90 synthetic without it and got “chatter.” Added it and no more noise. I have also used “Positrax” from Wallmart and Advance Auto, but I got better results with the OE additive.

 

yeah i don't know why you guys are adding it to non-limited slip type differentials...all it is is a friction modifier which ADDS friction so the clutch packs an work correctly