Need help ASAP: Does Mobil 1 diff oil need the friction modifier?

[trukk]

Guys,

I heading over to Lindsay in the morning and then off to VIR. I'm having them change my fluids (engine oil, diff, tranny).

6.5 qt Mobil 1 Synthetic 5w30 for engine.
4.0 qt Mobil 1 Synthetic ATF for the tranny.
2.0 qt Mobil 1 Synthetic 75W-90 Gear lube for the diff.

I looked at the faq, and did a search, but could find out if the Diff lube needs the GM friction modifier added to it or not. Can you guys let me know ASAP, so I can advise the shop tomorrow.

-Chris

P.S. Also having Nels' rear strut brace installed, and picking up some HP+'s to throw on the front calipers.

[JonCR96Z]

Amsoil doesn't require it. Not sure about the Mobil. If you don't get any answers then just have them put it in anyway, it won't hurt anything to have it.

[Ak Jim]

I added the friction stuff when I put in Mobile 1 in the diff. It is perfectly fine to add it if it is not needed, but if you don't add it and you need it there could be problems.

[RobWilson]

Yes. When in doubt, use the friction modifier.

[trukk]

Thanks guys.

-Chris

One a side note: One time while I was having some private time with myself , I added friction modifier to my normal lube, and got a real bad blister on my hand.

[JonCR96Z]

Originally Posted by trukk

Thanks guys.

-Chris

One a side note: One time while I was having some private time with myself , I added friction modifier to my normal lube, and got a real bad blister on my hand.

Doesn't appear to have helped with your whining either.

[darkman]

Originally Posted by trukk

Thanks guys.

-Chris

One a side note: One time while I was having some private time with myself , I added friction modifier to my normal lube, and got a real bad blister on my hand.

Your hand blistered first? How odd.

[trukk]

Quick update.

BIll added the friction modifier. 500+ miles later, and all seems well in rear end land.

-Chris

[C66 Racing]

Chris,
Realize I'm catching this late, but for future reference, Mobil 1 75w90 doesn't require friction modifier. This from their website:

"Mobil 1 Synthetic Gear Lube LS 75W-90 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."

Like the AMSOIL Severe Gear Extreme Pressure Synthetic 75w90 that I use in my Corvette Z06 on the track and in my 06 CTS-V, the Mobil 1 fluid already contains friction modifier. By adding extra modifier, you aren't likely to break or hurt anything, but you are probably losing some performance out of your limited slip diff. With too much friction modifier, the clutch plates in the diff will slip more than designed, so you are getting a less limited slip diff. This will cost you a little bit out of slow speed corners like the one at VIR with the tree...

For fluid with friction modifier already in them, my recommendation is to add the fluid withou the modifier and try it. If you get no diff chatter, then you are fine. If you get diff chatter, then add a bottle of friction modifier.

[trukk]

Originally Posted by trukk

Quick update.

BIll added the friction modifier. 500+ miles later, and all seems well in rear end land.

-Chris

And...1500 Miles later, the rear diff is LOUDER THAN HELL.

FLUCK!!!!!

-Chris

[lasciVious]

Originally Posted by trukk

And...1500 Miles later, the rear diff is LOUDER THAN HELL.

FLUCK!!!!!

-Chris

I used it too with the mobil1 ........ only got a few miles on it should I let it out?

[C66 Racing]

Originally Posted by lasciVious

I used it too with the mobil1 ........ only got a few miles on it should I let it out?

Personally, I wouldn't bother. A lot of Corvette guys add extra and I can't recall reading about anyone that had problems as a result.

[trukk]

My Clutch packs are binding, when I go around low speed corners. It'
s really loud. This just started about 1000 miles after this fluid change. WTF?

-Chris

[lasciVious]

Originally Posted by trukk

My Clutch packs are binding, when I go around low speed corners. It'
s really loud. This just started about 1000 miles after this fluid change. WTF?

-Chris

I heard my diff for the first time last night,,, is it the mobil1 or the additive?

[ewill3rd]

Chris, when are you coming back in?

I am busier than even I can believe right now but you know we'll work you in when you are ready