School me on CVT Fluid

[Sleepeyes]

So I understand:
CVT Fluid is WAY different than ATF because CVTs rely on metal to metal friction with their belts/chains
Every car manufacture uses their own spec even when the transmission can be found in multiple brands (Jatco JF015E for example)
Every car manufacture recommends their own maintenance schedule (or lack there of, ex Jatco recommends changing the cartridge filter and doing a drain and fill often, no mater the driving conditions, but Mitsubishi pretty much pretends that the filter doesn't exist and that the fluid is a lifetime fill unless you are in the "severe" maintenance schedule)
There are aftermarket fluid brands that meet manufacture specs BUT there is a lot of fear about using them despite US Law

What I would like to understand:
How is CVT Fluid different from ATF? From a base stock and additive perspective?
Is there actually a difference between Nissan NS-3 and Mitsubishi J4? If so, could that be why the same Jatco transmissions fail more often in a Nissan vs a Mitsubishi?
In CVTs that are a hybrid with a 2-speed automatic (JF015E), how can a fluid that is so different from AFT also handle the 2-speed gear box as well?

 

[Schmoe]

Great question....just got our first CVT and would be interested too.....calling MoleKule.....he knows ALL.

 

[CharBaby]

I am interested to learn more as well.

 

[ARCOgraphite]

I was all over this last year at 30K miles. I have all the viscometrics on my PC at home for the big brands. I recal it is a light fluid in the mid 7's cSt +/- with friction modifiers and anti-foamant adds.

All over the web, Nissan guys doing their own changes appear to have had good luck with Valvoline CVT fluid.

I'm under warranty and given nissan's interest in this trans longevity I went with SHOP changed (pan D&F) NISSAN fluid though it appeares to be the Wrong SPEC FOR THIS OLDER TRANS (should be NS-2 factory shop manual and OM lists NS-3 ) Given Valvoline lists ,AFAIK, NS-2, NS-3 compatibility on the bottle, you could assume the NISSAN fluid is reverse compatible.

I will say after my drain and fill I am seeing a TON of foaming on the dipstick and some odd behavior or the trans -- not holding low rpm under moderate throttle as it had done prior to fluid D&F.

 

[JeffKeryk]

I have serviced 2 CVTs:
2013 Accord at about 25K miles; used Honda HC-2 per Honda
2015 Altima from Hertz, 80K and 85K, Valvoline Synthetic CVT fluid (calls for Nissan NS-3). First time fluid was black, 2nd time not so bad. Runs like new, smooth and strong.

 

[slacktide_bitog]

The Prius hybrid CVT isn't really a CVT, and it uses regular Dexron/T-IV/WS type ATF. In fact, if you buy CVT fluid, it will say on the bottle not to use it in the Prius.

The fluid itself is rarely a reason for a transmission failure, whether it is a CVT or any other type. The only fluid-related failures are from going hundreds of thousand of miles without ever changing it. Most cars go to the junkyard on their factory fill transmission fluid

 

[nthach]

A regular CVT does have a torque converter and clutches(TCC at the least) as well. With the motion of the pulleys in the CVT changing pitch and the metal belt or chain flexing to comply, there's gonna be a lot of shearing happening. Nissan also had a toroidal CVT for RWD Infiniti applications.

There might be some friction co-efficient differences and other things at play - regular ATF is designed around friction(clutches) and kinematics. CVTs also need to focus a bit more on lubrication with the metal belt or chain but not so much to affect pulley friction.

 

[MolaKule]

Originally Posted by Sleepeyes
So I understand:

...What I would like to understand:
How is CVT Fluid different from ATF? From a base stock and additive perspective?
Is there actually a difference between Nissan NS-3 and Mitsubishi J4? If so, could that be why the same Jatco transmissions fail more often in a Nissan vs a Mitsubishi?
In CVTs that are a hybrid with a 2-speed automatic (JF015E), how can a fluid that is so different from AFT also handle the 2-speed gear box as well?


Some CVT's are coupled to a Torque Converter (TC) and even Lock-Up TC's. So then a fluid is needed for it and to provide cooling, proper traction coefficients, and to prevent wear between the linking mechanism and the Variators.

Here is a post that may help that I made in the ATF, Differential, Trans, Brakes, P/S forum:

...
Step-Shift ATF's and Friction Modification


The question of coverage has also been raised with the Dexron/Merc (Step-Shift) type fluids. If the Dex/Merc "Multi-Vehicle" ATF fluid has the proper friction modifier chemistries to support support a range of dynamic friction coefficients Mu(v), then they can provide a range of coverage and specifications.

Belt/Chain CVT's rely on another type of friction or coefficient of friction and that is called the, "Traction Coefficient."

This "Traction Coefficient" has to be within a certain range of values in order to properly transmit power and not let "slippage" occur, so special friction modifiers are part of the chemistry. The rest of the fluid contains base oils, Anti-Wear additives, and other components.

Now if the CVT fluid has the proper friction modifier chemistries to support support this range of "Traction Coefficients" then one fluid can cover Nissan NS-1 through NS-3 and other specifications.

As mentioned in other threads on ATF, whether it be for Step-Shift's or CVT's, ATF's are the most additized fluid in the automotive drivetrain because of these specialized friction modifiers.

The base oils used in CVT's are about the same as those used in Step-Shift transmissions.

The major difference is in the additives that are used to promote the "Traction Coefficients."

Here is a good review of Belt and Chain CVT's:

https://www.sciencedirect.com/science/article/pii/S0094114X08001432

 

[MolaKule]

Here is a Video from Weber State University's John Kelly on Push-Belt CVT's:

https://www.youtube.com/watch?v=PiwRUfFEc5k