How often to change ATF.....why?

[lomez]

I know a lot about engine oil, but transmission fluid, and the breakdown of it (does it really break down/degrade?).....kind of has me stumped. I guess I'm looking for an education on AT fluids, what they are, how they differ....and what breaks down. I know this is pretty open-ended. Thanks!

In one of my vehicles, I've got 130k miles....and other than checking the level (yes, this vehicle still actually has a dipstick), I've done nothing. Why on earth would I?

 

[azjake]

What does the owner's manual say? From my experience it varies widely by manufacturer and even model. Some don't even mention it in their service recommendation. Others say 30,000 or 60,000 miles. Mitsubishi recommends 60,000 mile changes for my Outlander.

 

[spasm3]

Clutch material gets into the fluid, I have no idea how efficient trans filters are. Its a hydraulic pressure system but i bet the fluid shears some.

 

[BigBuck]

I do a drain and fill every 30k.

 

[lomez]

Okay, let's put some of this to rest.....on one of, no several of my cars, I've been told by the DEALERSHIP, that they NEVER need to be changed. Even my 1965 Corvette specifically says "NEVER NEEDS TO BE CHANGED".

Again, IF someone is saying they do....why. One person said clutch material. That's a good point. But....wouldn't that make the fluid black? Thus if it's not black, why change? I'm looking for the chemistry of it. Fluids are not exposed to extreme temps (if not hauling something)...and are exposed to zero combustion or solvents. ?? why would they break down? how??

With brakes, I change fluid, but only because of contaminants in the fluid, such as dirt, water, rust particles, etc....in other words, I can see the contamination. If it were pristine clean....I'd never change. Why is a transmission different?

 

[BigBuck]

I have seen sludge and wear metals from my transmissions. Fluid turns black and smells burned out. Better out than in, Shrek would say.

 

[zeezee]

I've personally found wear metals attached to the magnet in transmission pans. It is quit probable that there would also be small amounts in suspension.

I suspect that a used ATF analysis would show a bigger picture. It is also possible that routine maintenance can prevent failure due to leaks. How many "normal" people do you know that actually check ATF levels or look for leaks? Many transmissions / transactions are sealed these days, and can't be checked without a complete drain and fill.

 

[Rand]

Originally Posted By: lomez
Okay, let's put some of this to rest.....on one of, no several of my cars, I've been told by the DEALERSHIP, that they NEVER need to be changed. Even my 1965 Corvette specifically says "NEVER NEEDS TO BE CHANGED".

Again, IF someone is saying they do....why. One person said clutch material. That's a good point. But....wouldn't that make the fluid black? Thus if it's not black, why change? I'm looking for the chemistry of it. Fluids are not exposed to extreme temps (if not hauling something)...and are exposed to zero combustion or solvents. ?? why would they break down? how??

With brakes, I change fluid, but only because of contaminants in the fluid, such as dirt, water, rust particles, etc....in other words, I can see the contamination. If it were pristine clean....I'd never change. Why is a transmission different?


Well the dealership is wrong.
for example your 1965 vette specified transmission fluid changes at 12000 mile intervals.

also you come in with your mind made up.. you are asking a question not trying to convince people??

 

[Donald]

ATF wears out from heat, contaminants and shearing. The major car companies wanted a competitive advantage over the others and used high quality ATF and said it never needed to be changed. Sounds good. It will get you to 100K with no change but its not the best for that expensive transmission. The red in the ATF is only a dye so it does not look like other fluids under the hood and the dye can disappear or not, and one should never go on color. If it smells burned, it needed to be changed awhile ago.

As others have mentioned the small chunks of clutch material wear off and are in the ATF. So are wear metals from the transmission and TC. Some will stick to the magnet, some get caught in the felt filter and some float around, maybe getting caught somewhere inside the transmission. My Magnefine filter had some small particles caught in the media and some metal paste that covered the magnet. After 40K miles on the filter.

The transmission is around $2500 these days. Your best bet since you seem skeptical is to pull a sample and send it to OAI/Ploaris for an analysis. A $25 investment. Depending upon how the UOA comes back you may not change it for awhile or wish you had changed it in 2011. Either way you will know more than you do now. And there will be facts involved rather than opinions. But don't bother showing the UOA report to anyone but BIOTG members (with a secret membership card) as they will not understand it, dealer included.

In my book, I feel its wise to use top quality ATF. I am a fan of Amsoil, but there are other top quality synthetic ATFs. And I added a Magnefine inline filter. Amsoil is good to 100K in normal and 50K severe. So here is probably the absolute best ATF you can buy and they do not say "never need to change it". What does that say to you?

 

[Rock_Hudstone]

Originally Posted By: lomez
Okay, let's put some of this to rest.....on one of, no several of my cars, I've been told by the DEALERSHIP, that they NEVER need to be changed. Even my 1965 Corvette specifically says "NEVER NEEDS TO BE CHANGED".

The average life expectancy of cars in 1965 was around 100,000 miles. Today well maintained vehicles can go 200,000+ mi, thats a lot to ask of a trans fluid.

Moreover, some vehicles have weak transmissions and lack trans fluid/filter replacement is almost begging for a premature trans failure.

 

[lomez]

Originally Posted By: Rand
Originally Posted By: lomez
Okay, let's put some of this to rest.....on one of, no several of my cars, I've been told by the DEALERSHIP, that they NEVER need to be changed. Even my 1965 Corvette specifically says "NEVER NEEDS TO BE CHANGED".

Again, IF someone is saying they do....why. One person said clutch material. That's a good point. But....wouldn't that make the fluid black? Thus if it's not black, why change? I'm looking for the chemistry of it. Fluids are not exposed to extreme temps (if not hauling something)...and are exposed to zero combustion or solvents. ?? why would they break down? how??

With brakes, I change fluid, but only because of contaminants in the fluid, such as dirt, water, rust particles, etc....in other words, I can see the contamination. If it were pristine clean....I'd never change. Why is a transmission different?


Well the dealership is wrong.
for example your 1965 vette specified transmission fluid changes at 12000 mile intervals.

also you come in with your mind made up.. you are asking a question not trying to convince people??


Well, as for the 'vette, I have the original owner's manual in front of me. "sealed lifetime maintenance free". Is that a lie?

But really, my question was about the CHEMISTRY that may require ATF to be changed in a modern vehicle. Other than the clutch material possibly being dispersed into the fluid (but I'd think you'd be able to see that and suspect that is a RARE event)....I haven't heard anything but "the manual says". Well the "manual" also says to bring your car in for a tune-up every 30k miles

But... anyone who does that is well...that's just $$$$ for the dealer.

My 2008 4Runner gives recommended service up to 120k miles. "Transmission" is not mentioned once.

 

[crazyoildude]

change the fluid because it does lose its additives.. i change mine every 30,000 miles and i have 240,000 on a Toyota and 322,000 on a 79 Cadillac (not a daily driver) with no problems at all with the transmission.
When my brother owned a transmission shop he always changed his and everyone else in the family because he would have to fix them for free.

 

[ahoier]

Originally Posted By: zeezee
I suspect that a used ATF analysis would show a bigger picture.
I don't know.....I've seen this question come up previously....to many/most around this neck of the woods, a transmission fluid used oil analysis is "boring" - more than likely due to the fact that there are soooo many different fluids available off the shelf...and the fact that these labs likely do not get as many AT UOAs.....so there's really not much that can be seen from the "Universal Averages"......now granted.....good idea if you suspect moisture/insolubles from the trans cooler getting into the fluid...

That being said....how should one perform a transmission dipstick sampling? Engine off....? Or engine on?

I know almost all vehicles say to check the level of fluid with the car on, and in park......BUT, siphoning fluid out of a "running" transmission doesn't sound smart to me....? Or am I overthinking this.....? lol....cause yea, I've been tempted to get a UOA on my A413 trans, to see how it's kickin....

 

[lomez]

Originally Posted By: Rock_Hudstone
Originally Posted By: lomez
Okay, let's put some of this to rest.....on one of, no several of my cars, I've been told by the DEALERSHIP, that they NEVER need to be changed. Even my 1965 Corvette specifically says "NEVER NEEDS TO BE CHANGED".

The average life expectancy of cars in 1965 was around 100,000 miles. Today well maintained vehicles can go 200,000+ mi, thats a lot to ask of a trans fluid.

Moreover, some vehicles have weak transmissions and lack trans fluid/filter replacement is almost begging for a premature trans failure.



but that doesn't explain the why part. I don't know what a "weak transmission" is. ?

 

[lomez]

Originally Posted By: ahoier
Originally Posted By: zeezee
I suspect that a used ATF analysis would show a bigger picture.
I don't know.....I've seen this question come up previously....to many/most around this neck of the woods, a transmission fluid used oil analysis is "boring" - more than likely due to the fact that there are soooo many different fluids available off the shelf...and the fact that these labs likely do not get as many AT UOAs.....so there's really not much that can be seen from the "Universal Averages"......now granted.....good idea if you suspect moisture/insolubles from the trans cooler getting into the fluid...

That being said....how should one perform a transmission dipstick sampling? Engine off....? Or engine on?

I know almost all vehicles say to check the level of fluid with the car on, and in park......BUT, siphoning fluid out of a "running" transmission doesn't sound smart to me....? Or am I overthinking this.....? lol....cause yea, I've been tempted to get a UOA on my A413 trans, to see how it's kickin....


interesting...ATF is interesting since everyone seems to try and make them (or call them) "proprietary". I seriously wonder if they are.

 

[lomez]

Originally Posted By: Donald
ATF wears out from heat, contaminants and shearing. The major car companies wanted a competitive advantage over the others and used high quality ATF and said it never needed to be changed. Sounds good. It will get you to 100K with no change but its not the best for that expensive transmission. The red in the ATF is only a dye so it does not look like other fluids under the hood and the dye can disappear or not, and one should never go on color. If it smells burned, it needed to be changed awhile ago.

As others have mentioned the small chunks of clutch material wear off and are in the ATF. So are wear metals from the transmission and TC. Some will stick to the magnet, some get caught in the felt filter and some float around, maybe getting caught somewhere inside the transmission. My Magnefine filter had some small particles caught in the media and some metal paste that covered the magnet. After 40K miles on the filter.

The transmission is around $2500 these days. Your best bet since you seem skeptical is to pull a sample and send it to OAI/Ploaris for an analysis. A $25 investment. Depending upon how the UOA comes back you may not change it for awhile or wish you had changed it in 2011. Either way you will know more than you do now. And there will be facts involved rather than opinions. But don't bother showing the UOA report to anyone but BIOTG members (with a secret membership card) as they will not understand it, dealer included.

In my book, I feel its wise to use top quality ATF. I am a fan of Amsoil, but there are other top quality synthetic ATFs. And I added a Magnefine inline filter. Amsoil is good to 100K in normal and 50K severe. So here is probably the absolute best ATF you can buy and they do not say "never need to change it". What does that say to you?



Excellent answer. Thank you!! That makes logical sense.

And yes....I'm the skeptical type. The trans in my import (rather not say the manufacturer) was $10k! ouch (nothing to do with fluids though)

 

[Zako2]

One theory I have heard is that it's not that the fluid becomes bad after a certain period. The problem is that it becomes saturated with particles as a result of transmission wear that you don't want to have in the fluid. If that's the case, you need to change not only the fluid but also the fluid filter.

How frequently to change the transmission fluid depends on the car. I know that the Ford Taurus online community and others that use Ford's AX4N/AZ4S transmissions follow the manufacturer's fluid change recommendations religiously (flush everything and change the filter every 30,000 miles). These transmissions are relatively sensitive to neglect and have earned a bad reputation for being prone to failure and then an expensive rebuild. Part of the reason for this is the owners who never bother to change the fluid.

 

[lomez]

Thanks for the ATF education! Makes sense...somewhat.

 

[MolaKule]

What vehicle and year?

Here is the chemistry of ATF:

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=729268#Post729268

What really killed some of the older transmission fluids were heat, which leads to oxidation of the fluid, and the shearing of the VII and the base oil. Oxidation can also degrade the FM's and the anti-oxidants which retard oxidation, forms varnish, which can clog valve passages and change internal pressures, and can also degrade the friction modifiers.


The more modern fluids such as DexronVI have vastly improved base oils, VII chemistry, oxidation inhibitors, and better friction modifier retention.

Still, 30,000 mile ATF changes are much cheaper than new transmissions.

 

[ahoier]

What gets me....on the topic of ATF and, the inherent "filter" change(s)......is how some of these quick lubes (Midas, Meineke, [censored] even Tire Kingdom....) offer "Transmission Flush" services.....they claim their machine can clean the gunk out/off of the filter.....now tell me how that works, without dropping the pan

I'm really curious....I understand the concept of "replenishing" the fluid, it basically slurps out the old fluid, and pumps in new fluid, until you got the proper concentration of "new" ATF.....but still, no filter change...? That just don't seem right I'd think the metals that were in there, are STILL in there, clinging for dear life onto that magnetic transmission filter.....correct..?