Been trying to figure out exactly what a "friction modifier" for a limited slip differential does, without much luck. But someone did point me to the following link that provides some insight to what a friction modifier actually is. Well somewhat, anyway.
https://www.machinerylubrication.com/Read/30336/friction-modifiers-use
https://www.machinerylubrication.com/Read/30336/friction-modifiers-use