All,

I am about to tackle my leaky pinion seal this weekend and I had a question around friction additive and gear oil. I purchased the Ford additive from Dr. Diff and I have a stash of Valvoline synthetic gear oil (75-90). The bottles say it already contains the additive for limited slip diffs.

My 8-3/4" rear has an Auburn cone type unit...should I add the Ford additive or not? Maybe use half? Is there such as thing as too much additive where it could have a determinantal affect?

Any insight is much appreciated!