Red Line 75W90 versus 75W90NS - friction modifier on an open diff?

[Steve E]

After reading the numorous recommendations for Red Line manual tranny fluid, I've decided to try some on my 2003 4cyl Mazda6. It's a front-wheel drive family sedan with an open differential, and I autocross with it regularly.

When it came time to shop, I found Red Line makes a 75W90 and a 75W90NS oil. The "NS" oil seems to be intended for open differentials, I think, presumably because it does not have a friction modifier. I suppose an unfortunate side effect of reducing friction in the differential would allow it to spin very freely, and with an open differential would increase the probability of a one-wheel spin. That's no good! I'd rather the differential be tough to turn, but perhaps friction in the differential will create too much heat, causing problems of its own. Spinning the inside tire IS a problem for me autocrossing. While Red Line says both oils will work with open differentials, I think the 75W90NS sounds more appropriate.

Still, I wanted to get a 2nd opinion before I buy. I know a bunch here swear by Red Line tranny oil, but which type is it that ya'll are using. What are the trade-offs? Does it come down to personal preference? Is the friction modifier what makes shifting so much smoother, and would I forfeit that? Does one wear better? Does the friction modifier decrease drivetrain loss? Does that even matter?

Again, this isn't for a limited-slip RWD car, but an open-diff FWD car. I wouldn't be making a big deal out of this, but some of the other threads here seem to indicate that using the wrong friction modifier can be terrible.

[ January 05, 2004, 10:30 PM: Message edited by: Steve E ]

 

[sprintman]

75W90NS is for GL5 transmissions with syncro's. Straight 75W90 has FM for diffs and LSD type diff's. RL also have the FM available seperately I believe for 'tuning' an LSD. Email Dave Granquist at RL for correct application.

 

[Jakebrake]

What type of fluid does the owners manual call for? Most new transaxles are not suited for 75w-90 gear oil. Maybe Redline ATF or MTL...but I don't know about gear oil. Does it call for a GL-4 or GL-5 fluid?

 

[Steve E]

I may end up calling Red Line tomorrow.

Yes, it calls for SAE 75w90, or (if I recall) 85w90 in warmer climates.

It also calls for EITHER GL-4 or GL-5. I guess I can use either of the above products, which again raises all my questions about what I can expect the pros and cons to be.

[ January 05, 2004, 11:11 PM: Message edited by: Steve E ]

 

[Jakebrake]

I think that you can get the best information about what suits your vehicles needs from Dave at Redline.

I'm just curious...is this a manual transaxle or automatic...and is the final drive lubricant kept separate from the transmission lubricant. Thanks.

 

[Steve E]

quote:

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Originally posted by Jakebrake:
I'm just curious...is this a manual transaxle or automatic...and is the final drive lubricant kept separate from the transmission lubricant. Thanks.

---

It's a manual tranny, and since I only see one thing to drain, I'll assume the final drive and tranny lubricants are one and the same.

I called the 800 number for RL today and the lady said she recommended the NS stuff. She said the normal 75w90 is "gear oil, and too slippery". I'm not sure that I had a chance to fully explain my question to her, though- the conversation was too quick. So, I fired off an e-mail shortly afterwards to the Red Line tech support address, making sure I included the proper details.

 

[unDummy]

Quaife/phantomgrip/..... are the solutions to tire spinning. Don't expect any fluid(other than superglue) to make a difference with an open differential. Better suspension tuning and tires might help too.

Mazda has been recommending gl4 or gl5 in their manual transmissions for years. Either they're engineering for it or they know the tranny will last past the warranty period with that(or whatever the factory fill is).

I still think that MT90 GL4 is the best bet for gearoil'd manuals.

 

[crossbow]

Thanks undummy,

Once again you bring a flashlight for all us mazda6 guys

.

(Cause you know...were in the dark).

Our trannies thank you

.

 

[Steve E]

Thanks undummy, you were right. Here's the reply I got:

Mazda allows either a GL-4 or a GL-5 type fluid in their transmissions and transaxles. I would recommend the MT-90 a 75W90 GL-4 synthetic gear lube.

The 75W90NS could be used though we find that the MT-90 can sometimes offer a little better shiftability. The 75W90NS is used in transaxles and transmissions calling for a GL-5 gear lube as well as clutch type limited slip differentials where maximum lock up is desired for racing use. In an open differential the lack of friction modifier won't affect the lock up as there are aren't any clutches fitted. The lack of a friction modifier wouldn't necessarily lead to more wear and tear, it might operate slightly warmer, but the friction modifiers if present would likely cause shiftability issues as it would be too slippery for the synchros.

I would recommend the MT-90, this is a transaxle and as such the lube is shared internally between the transmission and differential.

Regards, Dave
Red Line Oil

 

[JWRENCH]

I ran the NS type in my truck and it was fine.

I did read later though that the additive would help the gears slide easier on each other reducing the temp a few degrees more than the NS does.

[ January 10, 2004, 05:38 AM: Message edited by: JWRENCH ]