Nobody ever said the additive had anything to do with being Synthetic.
But most Synthetics have the additive already added to them.
and YES, Mobil 1 does have the friction Modifier in with it.
I think you need to do some resaearch before doing the call outs of who's right or wrong.

Here ya go:

Directly from Mobil 1's site.
Mobil 1 Synthetic Gear Lube 75W-140 LS contains special friction modifiers designed for limited slip-type differentials. In most applications, the addition of special LS (limited slip) additives is not required. For axles requiring the highest level of limited-slip performance, OEM specific LS additives can be added to this fluid.


From RP's website:
All viscosities of Max-Gear are formulated with hypoid friction modifiers necessary for use in clutch or cone type differentials. No additional additives are necessary.

From Amsoil's website:
AMSOIL SEVERE GEAR® is compatible with most limited slip differentials. If limited slip differential chatter occurs, add AMSOIL Slip-Lock™ friction modifier additive

Valvoline's website:
SynPower® Full Synthetic Gear Oil

Formulated for ultimate protection and performance

• Contains additives to assist in protecting gear teeth
• Maintains excellent low temperature fluid protection down to -50°F (-46°C)
• Provides outstanding thermal stability for cleanliness and longer service life
• Contains special additives to reduce chattering in limited-slip differentials
• Recommended for (conventional and limited slip) manual transmissions where an API GL-5 or MT-1 fluid is specified
• Protects parts from rust and corrosion
• Compatible with conventional gear lubricants

Pennzoil Synthetic:
HERE-reduces or eliminates chatter in limited slip differentials


Cheaping out for $5.... Why waste the $5 if it's not needed? I'm all about preventative maintenance but to insert something that isn't needed is a waste IMO, not to mention all Friction modifiers can't be treated equal just the same as motor oils or gear oils. Why spend $20 on a qt of Full Synthetic to buy the first bottle of Modifier that rolls off the shelf. Advance Auto carries Trans-x which is good stuff, but still, I think you get my point.

 

keyword..

 

I never disputed that fact brett. My arguement was that Mobil 1 LS has the additive in it already simple as that.

But, they do like to use words to their benefit such as OEM additives can be added which is a way for people to use their fluid and not get bumped out of warranty work.

All I know, is that I have used Mobil 1 diff fluid on 5 different vehicle and have NEVER had to add in the modifier including my 2008 Dodge Ram rear diff which is the same as everyone elses on here.

Also, the MOST part has to incorprate all kinds of clutch styles including aftermarket.

You may have one 2008 Dodge ram that needs it and another that doesn't depending on many factors, but it should NOT be added unless it's concluded that there is still chatter afterwards.

 

If you have to feel called out and insulted when someone says they don't agree with you, that's on you.

But you are still wrong. Mopar says to use the additive. They don't say "use mobil 1 or RP with the additive already in it."

Who gives a **** if the fluid is good in *keyword* "most applications?" This is a dodge ram subforum. All we care about is what's good in our chrysler 9.25 with factory lsd. And the factory says to use the additive.

 

I am not insulted because YOU were wrong!
How am I wrong? All I said was that Mobil 1 has the Friction modifier already in it and you said no. Who's wrong bud?

Ofcourse Mopar says to use the additive because additive IS needed and the Mopar diff fluid DOES NOT have the additive in it.

Out of all this, your still arguing what you were wrong on. Twist the posts any which way. YOU WERE WRONG!

Here's what I have always said;
If using Full Synthetic rear diff fluid such as Mobil 1 or RP which have the additive already in them, run them first to see if you have chatter, THEN add more modifier if it's chattering. WHy put something in if not needed.
It's definately a better bet to just add it because you don't know better, but that's a poor excuse.

 

Valvoline, RP, Amsoil, and Mobil 1 do NOT buy Mopar spec additive and add it in every bottle of gear oil. There for it is not within spec for mopar LSD.
Buy the synthetic fluid and a tube of Mopar LSD additive. and put the right stuff in.