Royal Purple, No Friction Modifier Needed?

[cadyshac]

Changing out my rear diff oil to Royal Purple Maxgear synthetic, it says friction modifier is not needed. I have read some conflicting reports so do I need friction modifier or not? (2013 2SS LS3)

Thanks,

Cady

[Mr_Draco]

Every differential is different. Some cars need a little extra, some don't. I use Royal Purple and have not needed it the last two times I changed mine. Do the change without it and drive around for a couple days. If you don't hear any chatter or noises then you don't need it.

[cadyshac]

I changed it tonight after work, no modifier added. Drove the car a little and seemed fine, I will just watch it for a few days.

[White_SS/RS]

I must have the most cranky diff in the world...Royal purple with an extra 8oz of friction modifier and it still groans!!!

[shibbs]

Originally Posted by White_SS/RS

I must have the most cranky diff in the world...Royal purple with an extra 8oz of friction modifier and it still groans!!!

That seems like too much friction modifier to me.

I returned my bottle of Royal Purple Max Gear on the recommendations of friends (and the local dealership) and went with Mobil 1 instead. No friction modifier needed.

[Stingr69]

I put the GM recomended 1/2 of a bottle of friction modifier in there before adding the Royal Purple gear oil in there. Seems to work fine but maybe a little stiff on cold winter days until the differential warms up. No real improvement so why switch to something more expensive? I used it because I had some in hand but would go back with GM fluid next time as it seemed to work better when the differential was cold. YRMV.

-Mark.

[black.]

Used royal purple in mine and had to put some extra friction modifier in.

[happycamper]

I changed mine with Mobil1 LS and needed the friction modifier, but yours may not need it. You'll know for sure within a couple days of changing if you need it... the sound is very noticeable when turning.

I would just get the friction modifier and add it. Otherwise, you'll need to drain some new stuff out to add the modifier.

[WHAMMO]

Originally Posted by Stingr69

I put the GM recomended 1/2 of a bottle of friction modifier in there before adding the Royal Purple gear oil in there. Seems to work fine but maybe a little stiff on cold winter days until the differential warms up. No real improvement so why switch to something more expensive? I used it because I had some in hand but would go back with GM fluid next time as it seemed to work better when the differential was cold. YRMV.

-Mark.

+1 on this.

My AcDelco fluid and friction modifier bottle worked perfect yesterday; no grind or sound. It was acting weird at very low speed when turning.

As for the quantity, the manual says its 900ml of fluid and 90ml of anti-friction. You dont need 2 quarts, its less than one bottle (it will overflow). And put the anti friction before the diff fluid.

[White_SS/RS]

Originally Posted by shibbs

That seems like too much friction modifier to me

Possibly, but I added little by little over time trying to quiet it. At first I didn't have any.

[shibbs]

Mine needed the entire quart bottle and about 2-3 ounces of an additional bottle I had lying around from a previous car. I let it drain very thoroughly though.