thoughts about ATF lifespan

[friendly_jacek]

Searching for Dex VI certification details I came across this informative document: dexron VI certification testing

According to that, Dex III is tested good for 20,000 acceleration cycles, Dex III (H) for 32,000, and Dex VI for 42,000 cycles in the GM 4L60 cycling test.

I know that this is a bit apples to oranges, but I use my corolla mainly to commute 10 miles with 20 intersections, or at least 20 acceleration cycles (not quite WOT like in GM test but sometimes close). So, should I expect Dex III (H) to last ~16,000 miles and Dex VI ~21,000 in my severe service?

I guess it sounds right as the shifting is very sloppy now at 52,000 miles, and I had ATF replaced (drain and fill) at 30,000.

Technically, I use T-IV, but sounds like it behaves like Dex III (H).

Any comments?

 

[bmwtechguy]

Yes, the new fluids such as Dex VI have better viscosity retention and longer lasting (better) additives. I think you are about right on the T-IV being similar in quality to the DexIII-H stuff.

I have seen T-IV get pretty beat up under your driving conditions in Alabama-like heat, here in SC. For longer ATF fluid change intervals you could install an aux cooler and inline filter. Switching to a compatible full synthetic fluid would also allow the fluid to stay in good shape, longer. I have done this to many vehicles and cut maintenance time and costs over the long haul. Plus the transmissions are lasting indefinitely when there are not design issues from the manufacturer.

Regular changes with OE fluids is much better than most people do, which is nothing....until it breaks.

 

[JHZR2]

That is an interesting way to look at it and consider things.

Thing is, we need to understand the difference in wear, shear, and fluid degradation between WOT starts and normal ones. It is pretty well established that an AT's life depends on how hard you use it and how hard you drive. Some of that is because of direct ear, power transmittal issues, etc., but some of it is due to degradation of the fluid, which is designed to mitigate some of those issues.

So the question is what is the split, and what are the implications?

I think that if you look back, youll see folks that changed dex II or III at, say, 30k intervals, and some got 100k and some have 300k with the AT still operating perfectly. Youll also find some folks that changed it at 60 or 90 or 120k, and still have a fine AT... but Id bet those folks are far more rare.

So what is "good" or passing over those WOT cycles? Some loss in viscosity? If so, then let's look at some UOAs of dex III, say (since it likely has the widest amount of data), and see how far folks drove to get to the lowest acceptable point in viscosity. Then Id cross that mileage with a few notional driving profiles, to get a rough estimate and correlation. From there, estimate what it means for yours.

Good luck,

JMH

 

[The Critic]

Not only is viscosity and oxidation part of the equation, but so are the frictional properties. I was told that in the past, the base oils would break down (loss of viscosity and oxidation problems) well before the frictional properties would become an issue. Now, with Group III base oils, the fluid's frictional performance had to be improved in order for them to last as long as the base oils.

Either way, 42,000 cycles translates to much more than 21,000 miles. I'm not sure what the exact number is, but I know that OEMs test their fluid under severe conditions for well past 100,000 miles.

 

[Donald]

So swap to synthetic ATF, install a inline filter, maybe a cooler, do UOAs and drive like there is an egg between your foot and gas pedal (people were told to drive that way years ago) and you will get the best life on average for the transmission you have.

How many people would switch to ATF and add an inline filter if someone would guarantee it would save a $1500 or $2000 rebuild? The return on investment would be very high for those two items.

 

[Whitewolf]

Actually 'synthetic' ATF is not necessarily the answer any longer, 20 years ago maybe.
These days a well formulated Group III based fluid can outperform a 'synthetic' in terms of thermal stress (base oil).
As the Critic pointed out though in modern formulations the base oils are often so good that the FM system gives in first.

 

[Donald]

Originally Posted By: Whitewolf
Actually 'synthetic' ATF is not necessarily the answer any longer, 20 years ago maybe.
These days a well formulated Group III based fluid can outperform a 'synthetic' in terms of thermal stress (base oil).
As the Critic pointed out though in modern formulations the base oils are often so good that the FM system gives in first.


Well Amsoil ATF is rated for 100K miles in normal use. The trick is to get rid of the wear metals which an inline filter will do. I am not saying I would go 100K miles without a UOA, but if it looked good at say 40K or 50K, I might change the inline filter and keep on going.

 

[parimento1]

The transmission filter combined with the magnets won't filter out most of the metal? My car has the foam filter (97 Avalon).

 

[Donald]

Originally Posted By: parimento1
The transmission filter combined with the magnets won't filter out most of the metal? My car has the foam filter (97 Avalon).


Thats why you need an inline filter like a Magnefine.

As other have said, the normal transmission filter is only a rock catcher.

 

[unDummy]

That Corolla is desperately needing better AT maintenance.

City driving, traffic, stop/go.... should be treated just like towing/fleet service.

Friendly_jacek, you need to have your ATF flushed. And, if you stick with Toyota T-IV, drain/refill it every 10k miles.

Any inline ATF filter can help. Suspended wear in the fluid can affect shift quality. Magnefine, permacool,.... are some worth trying.

Alabama hot long summers, along with stop/go driving.... could cause excessive ATF temps. A synthetic would be a benefit. An ATF temp gauge would help you determine whether a synthetic should be considered. An ATF cooler should be considered if sticking with T-IV.

 

[rkpatt]

Lubegard red added to the recommend fluid for the vehicle (final fill) will help protect the fluid from thermal breakdown .

 

[Donald]

Originally Posted By: rkpatt
Lubegard red added to the recommend fluid for the vehicle (final fill) will help protect the fluid from thermal breakdown .


But not needed if the ATF is synthetic.