8.8 posi and Lucas Syn. Lube
 

We drained the old stuff out and replaced it with Lucas Syn. we did not add the Ford additive. Should we? It doesn't chatter around corners. At the dragstrip, a couple of times when we did burnouts , the driver's side stopped spinning with the pass side. Does the additive help in a case like this or do we just need to get the new clutch and shim kit from the dealer? What is the part # to ask for? (Explored Rear, 3.73.)
Thanks Guys

I would add the friction modifier. I think its necessasary.