Observations with Royal Purple

[babytiger]

I changed the rear diff fluid at around 2100 miles to RP 75W90. It clearly states on the bottle that it contains the friction modifier, so I didn't add any. After changing the fluid I immediately noticed a skipping or chattering noise at low speeds in reverse and going forward making turns. It wasn't a metal sound more like a rubbing, kind of hard to describe.
Yes, I did the figure 8 method after putting the new fluid in. I chalked it up to being 'normal' mainly because I hadn't paid much attention BEFORE changing the diff fluid.
Fast forward to 5000 miles and I had planned on changing the rear diff again. I again went with RP BUT this time I added the friction modifier off the shelf at O'Reillys. The drain plug had very minimal debris on it at this second change, in fact less debris than the first change.
Let me say that after installing RP AND the friction modifier the noise is COMPLETELY gone.
So for me, RP WITH the modifier is the way I will go from now on.
Thanks for letting me share.

[Avenging Orange]

Interesting, the product didnt perform as promised, and you still use it?
I paid $9 for lucas non synthetic with friction modifier included and I've had no issues........and I didnt even have to drive in circles or figure 8's.

[babytiger]

The product didn't promise me anything. As stated in my thread title, it was my observation.
I also see you're not using factory recommended weights for your oils, obviously you have had products not perform as promised.

[Avenging Orange]

I figure if something 'clearly states on the bottle that it contains the friction modifier' but you get 'skipping and chattering noises' and have to 'add friction modifier' to the next change. I'd say the fluid didnt do or have what it promised.
And no, I have had no products not perform as promised because I dont buy 'hype.'
As stated in my sig.
Was'nt being nasty, was just making an observation of your observation.

[babytiger]

Avenging Orange, no worries. I'm not really a 'buy into the hype' type of person either. And no real brand loyalty either. I had used RP in the past in other capacities and had been happy. Thus my persistence in finding out what was wrong, for lack of better words. I use Amsoil in my motorcycle, Castol in my Chevy truck and no doubt will try several other brands throughout the course of the Camaros life.

[clg_98ta]

I used the RP w/o additional modifier about 2 years ago, and have never had any noise. Not sure why you had a problem, perhaps you didn't get it worked into the clutch pack well enough the first time.

[babytiger]

Cig, that is quite possible.

[PsychoZL1]

I used RP in the rear diff of my LT w/o adding the friction modifier. It was a little noisy for the first 20 miles or so and then it was fine after it worked into everything!

[LS3 SS]

Just put RP Max Gear in my Camaro today w/ Friction Modifier..."Thought" I heard noise when driving, but then remembered that I never paid attention to listen for noise before so I was probably listening to road noise of the tires. So far, no noise, no issue.

[NavyDood]

Adding extra friction modifier to ANY dif fluid that "says" it has it in it already is not going to hurt a thing and is needed in some cases. Not all differentials react the same coming off of the exact assembly line. In a perfect world with the rearends being multi produced by the masses on the same assy line, that doesn't mean crudola. They can and will react differently. The OP did the right thing.

[NFERNOSS]

Not sure why any of you aren't just putting in the Dexron LS used in the Vettes, that GM finally figured out works to eliminate the clutch chatter. If still under powertrain warranty, which I'm sure many of you still are, it can be done free of charge, problem solved. I would hate for any of you to have an actual rear diff failure, then bring it to the dealer with RP in it, which I can spot from a mile away, along with knowing if you have changed it out with fresh lube before bringing it in. Just saying!

[sprint17]

On my ls, I put motul 300 75-90 and added the 2.5oz of modifier and it works great. Motul 300 does not come with friction modifiers. When I change it next we have some diff oil from the craftsman truck I might use. But as of now I have no noise or chatter.

[babytiger]

Originally Posted by NFERNOSS

Not sure why any of you aren't just putting in the Dexron LS used in the Vettes, that GM finally figured out works to eliminate the clutch chatter. If still under powertrain warranty, which I'm sure many of you still are, it can be done free of charge, problem solved. I would hate for any of you to have an actual rear diff failure, then bring it to the dealer with RP in it, which I can spot from a mile away, along with knowing if you have changed it out with fresh lube before bringing it in. Just saying!

You would be hard pressed to find a dealer that would change out your diff fluid 'free of charge'....

If the proper weight RP is in the diff, no warranty claim could be denied. It is safe to use non GM fluids in your car. Properly trained, and that being the key, techs can determine if a 'fluid' caused a failure.

[NavyDood]

Originally Posted by babytiger

If the proper weight RP is in the diff, no warranty claim could be denied. It is safe to use non GM fluids in your car. Properly trained, and that being the key, techs can determine if a 'fluid' caused a failure.

Exactly. Your wasting your time with the "so called" techs that come here on C5. True 100% synthetic Group IV or Group V fluids can be be bought for half of what the inferior Group III synthetic GM fluids will cost you from the dealer. Always have some extra differential fluid friction modifier on hand no matter if it is supposedly already premixed in the new fluid you are using.