Based on test date from field vehicles and accelerated lab tests. Some of the data is publicly available if you look for it, I believe there's even some related linked articles here at CL
There are formulation differences that end up with variances in the durability and reliability test results.

Again, if you are going to change it similar to past vehicles then it won't matter as much the formulation differences, but it's not necessary to change it within the design life.

 

"Lies" is a strawman, additional/conflicting considerations is the reality.
It's just a matter of logic that the manufacturer of the transmission doesn't have overall vehicle maintenance costs to consider in their service recommendations, thus you're more likely the get the recommendations of the actual engineers from Aisin.

 

Unless you carry a car top carrier, or drive around with a few passengers, or tow anything, or idle for a while.



It's a known fact that the primary failure mode of the A760F is due to internal pressure loss from valve body scoring, which is caused by old, depleted fluid carrying wear debris.
Vague "Lifetime fill" ATF recommendation combined with no auxiliary transmission cooler (in most cases) can be blamed for virtually all of the A760F transmission issues, IMO.
I doubt Toyota powertrain was on board the "lifetime fill" verbiage, I would bet a lot of money that this came about from marketing and accounting.

 

faulty logic, the supplier agreement has stipulations for both parties. both sides align on the maintenance schedule. The mfg creates the requirements, the supplier spec calls out what is required in order to meet the design life requirements. Vehicle maintenance costs are on the supplier when the part fails and it was maintained per aligned spec.
way off topic, and not worth the time to explain so many things on how this actually works to some that want to merely be correct instead of learn.

to the OP: in simple terms, its called lifetime but isnt forever as someone else stated. it is recommended to change once you hit the design life or even end of warranty period. if using aftermarket fluid, then follow that fluid mfgs advice on the schedule once their fluid is in the vehicle. Toyota formulation has differences, some designed for new parts unlike aftermarket. by the time you change your fluid you won't have new parts, therefore differences wont have any noticeable impact once on an aftermarket schedule.

 

thanks for providing the manual evidence for what i stated here
https://www.clublexus.com/forums/gx-...l#post11981631

 

Incorrect on all counts, the logic is sound and is based on the fact that I manage an account for one of the largest OTR companies in the US and deal with OEM warranty every day.
There are 3 OEMs that have created custom service intervals for us strictly due to our purchasing power, against the recommendation of said OEM's powertrain engineers.
Automotive service recommendations often deviate from powertrain's preferences/recommendations, for reasons already stated.

This is what faulty logic actually looks like, IMO:
...at least when the people that sell the fluid also designed and manufactured the transmission.

Please describe the Toyota formulation differences, as the self-appointed resident educator and tribologist.

While we're at it, I love to see evidence supporting this opinion, specifically the part I put in bold:

 

^ ... completely understand ... it's called communicating to "audience". Hope you communicate better soon.

 

I'm enjoying the arguments from both sides. I will say that I have yet to read an actual "statistically valid" study done (e.g., designed experiment) where there is substantial proof of the relationship between aging fluid and component failures. It is all anecdotal, or perhaps correlation (if anything).

For example, I copied a quote from above: "It's a known fact that the primary failure mode of the A760F is due to internal pressure loss from valve body scoring, which is caused by old, depleted fluid carrying wear debris." This is a hypothesis not a known fact. If you think it is a fact, please present the data and data acquisition strategy to conclude a causal relationship exists.

I think what is clear, as far as engineering goes, engineers do not get time to study their designs as sufficiently as possible before their designs are released. I have worked with several fortune 100 companies (including aerospace) teaching statistical methods to design engineers. The number 1 metric driving their behavior is release date. When you don't have time to study the factors that affect reliability (this is not easy. many accelerated mechanisms are used, but none are foolproof), you make choices to meet the release date. Given a factor, such as fluid, MAY have an affect and there is no added cost to the design, most if not all engineers would suggest changing the fluid.

I do recall seeing data presented on another forum (Porsche, I think the user name as Tool Pants) from a reasonably constructed study regarding oil. The study concluded synthetic oils formulated today can perform far beyond the "life" recommended by manufacturers (There was no measurable loss of oil performance through 25K miles). But, of course, all studies have an inference space (the area over which we have confidence in drawing conclusion). If there is a change in inference space, all bets are off.

I think most folks suggest the cost of doing fluid replacement is minimal compared with the cost of a catastrophic failure. Although, there is a substantial increase in screwing something up (damaging parts, re-assembly issues) and likely environmental issues for disposing of used fluids.

 

Personally I would replace the diff, transferee and transmission, its an easy one to do your self.

Replace etc diff and TC t 30k and 60k, at 30k there was some grime/sludge in the diff oil. at 60k that was reduced significantly, will see at 90k how it looks, but for me I would rather have oil with less sludge in my diffs and TC. Will it impact total lifetime I do not know, but it makes me feel more at rest that it was done.

As for transmission, I'll add the hem cooler in the next few weeks, at that time I'll do a drain and fill of the transmission.

Did a oil change on our ML350 a moth ago at 90k, and to be fair, the oil still had the bluish hue from MB oil, but you could tell is was not clear blue as new oil, (makes sense after 90k miles), again, will it extend lifetime I do not know, but it makes me more comfortable that it was done.
Next for ML is the rest diff change as well.

But again, it is up to you if you want to replace or drive with it as is, personal decision.

 

Hypothesis with correlative evidence would be the accurate terminology.
I will never perform statistically relevant field study on the A760F to prove this hypothesis, just as I doubt you or anyone else on this forum ever will.

What isn't hypothesis is the primary point of failure, and I personally will not disregard correlative evidence for an argument from ignorance.
For the average end user I don't think a field study is necessarily needed to recognize that sheared ATF carrying debris will most likely exacerbate valve body bore wear.

IMO, Disregarding lifetime fill ATF claims is just a common-sense precaution in the A760F's case, given it Achilles heel.

 

Are you the language police? So just to clear up your language, please don't use the word prove as it is impossible to prove anything true. Statistical lesson for the day.

"In god we trust, all others bring data", W. Edwards Deming

 

Sir, I just clarified my language.

Regarding proving a hypothesis, it seems you are the one that has taken up the mantle of language police here.
Neither you nor I are writing a dissertation or white paper in this thread, there's no need to be so pedantic.

 

You have no idea what you talking about. Pick up a math/physics/chemistry book and educate yourself.

 

I've never seen an Aisin transmission die that has seen regular maintenance. I've seen many die that got none.

 

Im sure you can use the internet to research the differences if you really want an answer. the differences are not opinion, they are fact determined by data analysis. in the lab research is the first thing we do as the initial benchmark studies. this was even posted here on CL a few years back if you really want to know you can search here..
im not a tribologist but i did manage a tribology lab at one of the other auto mfgs i worked at. we actually call them failure analysis and materials engineering labs, with tribology as one of the areas.
the tribology tests are mostly focused on the materials, this lifetime fluid issue testing isnt done at a coupon level or in a tribology lab. we do this in durability and reliability labs in order to more closely replicate real world results.
i am involved in the supplier agreements on eom mfg chargebacks on design life fail parts so what i say isnt logic, its fact. if you're using logic on this and not fact then this seems to be speculation and not experience.
Your knowledge based on what you havent seen does not mean that it isnt done; it merely means that you just dont have the experience.