i have 05 w/975-373 LS and i am getting some clutch shutter on normal take off. Now i recently changed to Royal Purple, and i did not add any extra additive. I read somewhere on this site where someone said you still need some additive cause RP dosent have enough in it, or whatever the reason. Now willl any brand be o.k., and would I add 1/2 tube or full tube, im concerned about mixing brand x with whatever RP uses. thanks in advance...rossford

 

no one has added extra friction modifyer (like Ford's XL-3) to the RP 85/140 synthetic? I'm not really sure if my clutches are slipping on one side or both. It has 28k, and I understand the factory LS wears out fairly quick,,,,it even does it on a straight take off. Just enough to hear it, not bad, but i'm also concerned about the clutch wear particles in the oil. thanks rossford (05 scab 9.75)

 

What you are thinking of is: Additive Friction Modifier

However, Royal Purple already has the friction modifier added. No need for additional friction modifier. In my rear ends, I've used Royal Purple, Lucas Oil, and Red Line, all without any issues. Your problem is not the fluid. If you've got the 5 year warranty, have your dealership take a look at it and service it for free.