Which Differential Oil?
 

Which Diff oil should I use?

Redline 75w90NS Gear oil quarts and cases (w/o friction modifier)
or
Redline 75w90 Gear oil quarts and cases (w/friction modifier)

I am not sure by what is meant by the "friction modifier".

Use the one with with friction modifiers (ie, non-NS) version for your rear differential. See descriptions from Redline's website below.

75W90NS GEAR OIL

This GL-5-type geal oil doesn't contain the friction modifiers for limited-slip hypoid differentials. This makes the transmission synchronizers come to equal speeds more quickly, allowing faster shifting and much easier low-temperature shifting. Can also be used in racing limited-slip differentials where weak spring design causes too much wheel spin.

75W90 GEAR OIL 1 QUART

Our most popular gear oil, this is the preferred product in nearly all car and light truck differentials, both conventional and limited-slip. 75W90 is preferred for most racing applications. It contains friction modifier which is recommended for limited-slip units. 75W90 Gear Oil can be used in many transmissions and transaxles; however, other Red Line lubricants have better frictional properties for rapid synchronization. Exceeds API GL-5.

Would using the 75W90NS (without the friction modifier) harm the Differential at all? Are there any drawbacks to using the non-friction modifier oil?

I believe the friction modifiers are used in clutch style limited slip systems. Corvettes continue to have a problem with sticking plates, hence their need for Friction modifiers in the gear oil. The Z has a sealed Viscous system so the fluid type has no impact there.

Thanks for the info everyone!

I have Redline 75W90 in mine, and it works fine.

motul

One would think that we should use the NS designation since it allows for "transmission synchronizers come to equal speeds more quickly, allowing faster shifting and much easier low-temperature shifting". Even Modshack stated that it "should not" make a difference as to which one to utilize.

I think I am going to order the NS designated oil and try it out and let you guys know how it goes.

75W90NS GEAR OIL

This GL-5-type geal oil doesn't contain the friction modifiers for limited-slip hypoid differentials. This makes the transmission synchronizers come to equal speeds more quickly, allowing faster shifting and much easier low-temperature shifting. Can also be used in racing limited-slip differentials where weak spring design causes too much wheel spin.

Remember, No Synchronizers or Clutch type LSD's to worry about with the Z. Spec's say use a GL-5 fluid...

I used Eneos: Nippon Oil | ENEOS MT Fluid

http://www.eneos.us/images/products/bot-MT.jpg

So in your experience the Nippon Oil | ENEOS MT Fluid is superior to the Redline 75W90NS?

Who knows? It is a high spec GL-5 ubricant sold by the largest oil Co. in Japan though. Several of my friends and the local Rice shop have had good experience with it..

I prefer Redline, but Eneos will due the trick

It might be correct that the 370Z differential doesn't need the friction modifiers in the regular 75-90, but it can't hurt it. I don't think you'll benefit from using the NS version over the regular GL5 75-90 (w/friction modifier)unless you were to use it in a Manual transmission. The NS is designed for either non-LSD's or MT's requiring GL5. Any reason you need the NS version? Just curious because the benefits you cited would only be for when it is placed in the MT. (but our MT requires GL4, the MT-90 version).

I have a Manual Transmission which is why I brought that issue forward. Someone else sited the differences between the GL5 and GL4 specs in another thread, and I thought it was determined that GL5 was a higher speced product, which led me to believe you could use GL5 in place of GL4. Is that a correct assumption?

Are you talking Trans or rear? If you read the other thread you'll see I used it in both despite the critics. Eneos is marketed for it and has been formulated to deal with the sulphur issue. Not all GL-5 spec oil has apparently. Car is running and shifting great. If you're not sure, then MT-90 in the trans, and a GL-5 spec in the dif.