CVT Fluid Properties versus ATF Properties

[dkryan]

To piggyback a recent thread by ledslinger regarding "new ATF ....and what the mfr. is looking for....," I'd like to know the inherent differences between CVT fluid and ATF.

I know the difference between the two transmissions since I have both.

I'd like to know the difference in terms of composition of the fluids.

 

[MolaKule]

Originally Posted By: dkryan
To piggyback a recent thread by ledslinger regarding "new ATF ....and what the mfr. is looking for....," I'd like to know the inherent differences between CVT fluid and ATF.

I know the difference between the two transmissions since I have both.

I'd like to know the difference in terms of composition of the fluids.



The main difference is in the friction modifiers.

For a step-shift transmission, the coefficient of friction (dynamic coefficient of friction) has to change with the relative velocities of the rotating components as they engage and disengage.

In a CVT transmission, the friction modifier maintains a traction coefficient so the belt doesn't slip.

 

[dkryan]

Is one type of transmission more harsh on the respective fluid than the other?

That is, with all variables being consistent, e.g., annual miles driven, climate, driving style, etc?

I know several car makers advertise "lifetime" ATF in their vehicles or a fluid change at 100k miles.

Nissan wants us to have a drain and fill of the CVT pan every 40k miles using NS-3.

I already had that performed at 10k miles out of habit, as I normally do with a conventional transmission, though it's actually a full transmission exchange with Amsoil.

 

[Doublehaul]

Tough to say on the fluid but I've not been impressed with cvt's. Longest I've seen one go was about 135k on a ford free style. I had 2 '14 subarus and both started experiencing cvt issues around 50k. I traded them in before things got too nasty. Iirc they had "lifetime" intervals. VERY expensive to overhaul

 

[ksp7498]

Originally Posted By: Doublehaul
Tough to say on the fluid but I've not been impressed with cvt's. Longest I've seen one go was about 135k on a ford free style. I had 2 '14 subarus and both started experiencing cvt issues around 50k. I traded them in before things got too nasty. Iirc they had "lifetime" intervals. VERY expensive to overhaul



The lifespan of CVTs seems to vary wildly from unit to unit, but honestly this is no different from traditional automatics. How many A604's and AOD's and Honda V6 transmissions died before 100k? My father has a Ford 500 (basically the same car as your freestyle) with around 190k on the original CVT and still going strong. But that's probably longer than normal. I seem to hear about the Nissan ones dying the most.

 

[dkryan]

Originally Posted By: ksp7498
Originally Posted By: Doublehaul
Tough to say on the fluid but I've not been impressed with cvt's. Longest I've seen one go was about 135k on a ford free style. I had 2 '14 subarus and both started experiencing cvt issues around 50k. I traded them in before things got too nasty. Iirc they had "lifetime" intervals. VERY expensive to overhaul



"........I seem to hear about the Nissan ones dying the most."


Yeah, that's what concerns me. I had hoped by the 2014 model Nissan had resolved any issues. Time and mileage will tell.

 

[Whitewolf]

It depends on the individual design. If there is a launch clutch then the friction for that has to be correct of course. Then, if it's a belt type for instance, one needs the appropriate friction in the areas, element/sheave, element/element, band/element, band/band. Some of those requirements are a difficult balance in terms of friction modifier selection. All of that in addition to the usual attributes such as viscometrics, shear stability, anti-wear etc.
I would say, and I'm not alone, that CVT fluid is much more of a formulation challenge than ATF.

 

[MolaKule]

Originally Posted By: Whitewolf
It depends on the individual design. If there is a launch clutch then the friction for that has to be correct of course. Then, if it's a belt type for instance, one needs the appropriate friction in the areas, element/sheave, element/element, band/element, band/band. Some of those requirements are a difficult balance in terms of friction modifier selection. All of that in addition to the usual attributes such as viscometrics, shear stability, anti-wear etc.
I would say, and I'm not alone, that CVT fluid is much more of a formulation challenge than ATF.

 

[dkryan]

Originally Posted By: MolaKule
Originally Posted By: Whitewolf
It depends on the individual design. If there is a launch clutch then the friction for that has to be correct of course. Then, if it's a belt type for instance, one needs the appropriate friction in the areas, element/sheave, element/element, band/element, band/band. Some of those requirements are a difficult balance in terms of friction modifier selection. All of that in addition to the usual attributes such as viscometrics, shear stability, anti-wear etc.
I would say, and I'm not alone, that CVT fluid is much more of a formulation challenge than ATF.


Which is why, no doubt, Nissan went from their NS-2 fluid to NS-3 in the 2014 model year.

 

[Anthony]

My moms 07 Altima CVT, and the car in general has been almost flawless. Not a single CVT hiccup. Car has a 136k, and is showing no signs of weakness. I change the CVT fluid every
25-30k.

You hear of more Nissan CVT issues because Nissan has more on the rd than anyone else by a HUGE margin. They sell over 300,000 Altimas a year, and then add their other cars that have CVT's

There will always be some bad apples, but overall I believe it to be reliable in most cases.