I just purchased some pennzoil gear lube for my rear diff and it says on the container "it does not need a limited slip top treatment nor is one recommened". I picked up a bottle of ford friction modifier, think i should go ahead add it or leave it out?

 

I used Castrol Synthetic with the Ford Friction Modifier when I installed mine. Not sure if the bottle said to use it or not, I didn't even read it, but I put it in anyways. Almost 500kms so far and all is good. Not sure if the Penzoil stuff is much different, maybe someone else here has used that specific stuff.

 

I do not use the Friction modifier in my rear end. If i would have ahd a problem with chatter then i would have put some in.

 

GM Friction Modifier is one of the better ones out there belive it or not. ( I worked for Penzoil / Quaker-state and the gear heads there seem to think the world of it) I've been running it in my Mustangs and f-150. Never any problems