You guys add this to your oil in the rear diff??

thanks

 

Its a friction modifier. It makes your trak-lok work correctly. It was added when I changed my oil.

 

do part stores carry it or do i need to go the dealer?

 

Have to get it at the Ford dealer only.

 

wrong. Oreillys carrys it. At least they used to here. Speaking of which....I need to change my rear diff fluid tomorrow.

 

My O'reilly's doesn't carry it, and this guy lives in Canada. Instead of jacking around all over town, just go to the Ford dealer and buy it. Unless you like wasting a bunch of time.

 

I get my posi additive at my local race shop.

 

Did mine 8 months ago, because it was vibrating when doing turns from start or when hauling something. Put all motorcraft oil and put 2 bottle of additive instead of 1, 4oz each, I didn't have vibration since then. I was told that you can put any brand of oil but to use Ford friction modifier.

 

You need it with a limited slip. About $10 buck's for 4 ozs at Ford dealer's.

 

If you run Royal Purple you dont need it FYI