I came across this by accident on another forum...I thought it was interesting...

Toyota Automatic Transmission Fluid - Wikipedia

Careful - this is a sensitive topic... lol. Toyota and Aisin say don't use non-WS fluid and WS and Type 4 are not compatible or interchangeable. BUT... a lot of people will argue that other fluids are fine in the A750f. Some toyota mechanics have suggested that the clutch materials changed when they moved from serviceable to WS fluid transmissions. I have no evidence either way. Short of getting some information directly for Aisin, I don't know if we'll ever really know. Toyota WS is cheap, so I have no idea why someone would not just use the right product. Frankly, I don't know why most people who change the fluid in a lifetime fluid transmission ever change it. There's no evidence anywhere I'm aware of that suggests that it offers any benefit to do. The second million mile tundra transmission lasted 792,000 miles without a fluid change before the third gear engagement developed a slip. The first one went over a million on the original transmission, but I haven't seen anything detailing whether it was ever serviced.

I watched a 30 minute video on how to check Toyota fluid levels for transmissions without a dip stick last night.

I don't know why I was watching but I did.

I know the feeling...some of those videos are like lava lamps...you can't help it...

Because it's not lifetime fluid.

When was the last time you had or read about an A750F going bad? Most transmission shops have never seen one. You can change the fluid every week or never, the results will be the same. There's no reason to ever change it unless you get water in it somehow or your overheat the transmission somehow. Both of those are really hard to do. That's why Toyota doesn't recommend changing it ever for most people.

This is a quote from TSB-0006-11 (I added the bold and underline, Toyota capitalized "NOT".)


World Standard Automatic Transmission Fluid
Required Tools & Equipment
SPECIAL SERVICE TOOLS (SST) PART NUMBER QTY
Transmission Fill System* 00002-11100-02 1
* Essential SST.
NOTE Additional SSTs may be ordered by calling 1-800-933-8335.
Important Information
• 100,000 Mile Maintenance Interval — Inspection only; ATF-WS does NOT require any flushing or changing during the life of the vehicle.
• The use of Genuine Toyota ATF-WS is recommended.
• The use of additives or aftermarket fluids that are considered compatible or substitutes may result in shift concerns and damage to the internal transmission components.
• ATF-WS is NOT compatible with T-IV or Dexron ATF.
• Containers storing Toyota ATF-WS should ALWAYS be sealed — If exposed to the atmosphere, ATF-WS may absorb moisture and potentially cause shift concerns if used in operation.
• One time use only.
• When performing repairs on ATF-WS equipped transaxles, it is important to use only new, clean ATF-WS when refilling the ATM.
• ATF-WS equipped ATMs may use the overflow type procedure — Any fluid drained from the overflow plug should be discarded following proper local regulations and never reused. Failure to do so could result in shift concerns and damage to the internal transmission components.

I quoted your comment about WS being Lifetime fluid. Please present Toyota doc that says just that -> lifetime

I just edited my comment above. TSB 0006-11 says exactly that and specifically do not change it unless there's an issue.

https://attachments.priuschat.com/at...TF_WS_info.pdf

I don't think you will harm it by changing it, but you're not helping either. Putting a non-WS fluid in may harm it. Apparently type 4 is too thick and causes cavitation in the fluid pump or something along those lines in cold temperatures. It also doesn't flow as well so the pressures in the hydraulic system that move the valves and clutches won't operate properly if you use WS in the transmissions in the model years after they've adjusted them for WS.

priuschat…..you're funny.

@Jetboy ,the difference is in Toyota’s definition of “lifetime” vs. an owner’s. Theirs: the warranty period, so 100K miles. Ours: until the wheels fall off, so God knows how many miles. Add to that the fact that no fluid, regardless of what it’s made of, can possibly maintain the necessary properties indefinitely. That’s not how the world works, especially in a hot machine with lots of metal moving every which way under constant stress.

I just don't see any failures when I look around. Sure, some transmissions have had issues, but very few and very infrequently. And there's no indication I'm aware of that any of the failures I've seen are related to the fluid being old or having not been changed. I'd bet less than 1%, probably less than .01% are ever changed. Yet almost 100% last as long as the vehicle does. Toyota says so. Aisin says so. I'll take the people who actually design and test the product's word for it. I trust them on the oil change intervals. And on the transfer case and diff intervals. I have no reason to dispute their testing on the transmission.

My last 4R I changed at 200k for no real reason than it seemed like an okay idea. Probably wasted the time and $. Anecdotally on the other side - my last Allison automatic that requires 15k oil changes with filters only lasted 80k miles before it spit metal chunks out. So... obviously frequent oil changes didn't help poor quality manufacturing.

If a fluid will last 100k miles, there's no reason it can't last 500k miles. Or a million miles. The lifespan is not indefinite - but it may be as long as the life of the vehicle. The breakdown is probably some version of logarithmic. Meaning if it lasts 100k, it probably also lasts a million miles. There's almost no difference between the two in terms of the oil condition.

Oh, you're throwing down the gauntlet here, you will get people coming out of the woodworks to fight now

This is probably the least understood part of the conversation, although it makes more sense to cap it at 300,000 miles, since so few vehicles exceed this number to create a large sample size.

If a thing is going to break, it's going to break early or consistently or both. If a thing is going to wear out, it will wear out according to a normal distribution, which is why tires may not give the same mileage to all customers, but Goodyear and Cooper and others can say a tire will last "40,000 miles" because they know the distribution of outcomes for tires. But things that don't break, or don't wear out, are hard to predict because there isn't a "normal distribution" to follow, and so anything that lasts 100k should be expected to last 200k, and anything that lasts 100k is more likely to last 200k than something new at 20k.

You make some valid points and you may be correct, IDK. But to me, there’s a significant difference between “lasting” X number of miles and adequately fulfilling a purpose. @Toffees mentioned tires and yes, a tire may last 70K miles but given the choice between driving on that set or new ones, I’ll take the new ones. Just makes sense that everything wears out. The variable is when the fluid’s effectiveness drops below acceptable and it’s tough to know that for certain.