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Discussion in 'SVT Shelby GT500' started by [email protected], Sep 5, 2017.
I used Motul 75W140 a little pricey but highly recommended by my mechanic. No issues thus far
bumping this thread to see if anyone else has recommendations.
Looking for anything in particular?
For the ford LSD i like royal purple and the added ford friction modifier.
My other choice would be amsoil with ford friction modifier
3rd is Mobil 1 with ford friction modifier
Thanks, those choices seem to be a pretty popular recommendation. My 08 came with an LPW diff cover and 3.73 gears.
Welcome. Sounds like someone made some smart choices on the rearend.
Do you really need to add the friction modifier when using RP gear oil? RP gear oil already has friction modifiers added into it from the factory.
I’ve added the RP both with the additional FM and without it. Noticed absolutely no difference either way. No additional noise from the diff without it.
So, we just got into an argument about this on the S197 forum. I wrote RP about whether FM was needed, and they wrote be back immediately to say:
"Thank you for contacting us. You should not need any additional friction modifier additive with our Royal Purple Max Gear 75W-140 (part #01301, quart bottle) in your 2008 Ford Mustang’s limited-slip differential.
All of our Max Gear oils contain an appropriate dosage of the friction modifier additive that for most OEM and aftermarket performance type limited-slip differentials, no additional friction modifier additive is typically necessary. It is rare that any additional LSD-FM (limited-slip differential friction modifier) would be needed with our Max Gear oils. Please keep in mind that LSD-FM actually takes away LSD clutch grip, which allows the clutches to release more smoothly on tight turns. A large over dose of the LSD-FM additive is not desirable as it could reduce the effectiveness of your limited-slip differential unit's operation (possibly result with “one-wheel peel”).
If a customer experiences a shudder on tight turns after doing a limited slip differential fluid change to our Max Gear oil, we will recommend taking the vehicle to a nearby empty parking lot and doing a couple of sessions of 10 slow and tight as possible figure 8s. The figure 8 procedure is often standard practice at car dealership service departments for limited-slip axle/differential oil changes. This works the fluid in between the clutches, and treats them due to the high differential in the wheel speeds. This normally will make the shudder in a limited slip differential that is in good mechanical condition go away.
If you are still experiencing a shudder on tight turns after doing the sessions of figure 8s and some normal driving, then you may need to add a cap full or two of some additional friction modifier to stop the shudder. Don’t dump the whole bottle in though, as you already have what is considered a normal limited slip differential-friction modifier dose for most applications. Limited slip friction modifier can be purchased at your local Ford, GM, Jeep, Dodge or Chrysler dealer parts departments or bought from a local parts store, they are all basically the same stuff. Remember to repeat the figure 8s each time limited slip friction modifier is added, if you do need to add any additional friction modifier.
Thank you for inquiring about Royal Purple, and have a great day!"
Very timely info. Thanks for posting!
For my personal taste i use friction modifier with RP