150,000 Miles OEM , 15 Year Old Transmission Fluid, Should I Change, Still Clear Red Color

From the article:

IF your customer’s vehicle is high mileage and has never had a complete transmission flush service or has only had the old transmission service of changing the filter, you might want to advise the customer and your shop management that there could be negative consequences.

Even the author of that article is admitting flushing isn’t always a good idea:


I bought my now gone 2005 Camry with 35K miles on it and even then the ATF was dark. Someone has changed yours. As mentioned, it has a filter inside. I changed mine a few times. Used Maxlife synthetic ATF and was shifting fine at 185K miles when I sold it. One time the filter kit I got from Autozone had an issue with gasket being a bit off, it developed a tiny kink on itself and I didn’t see it. It was not leaking for the first day but then when it was driven more, it opened up and filled my garage with red ATF. From that point, I bought the kit from the dealer to the tune of $55.

I’ve observed the example of contrary.
I helped to replace transmission to a friend of mine with mid-2000s Toyota Echo, he had 200K miles on it, mostly highway miles.
Fluid in the transmission itself looked red and fresh, but his final drive gear was worn to the point of making noise and shudder.
When we drained the fluid, it came out red and fresh… from the transmission itself, then we found ANOTHER drain plug on the final drive gear section.
Once we opened that, a black goo started to slowly emerge from there.
Dipstick would show the level and fluid in the bigger chamber- the transmission itself.
Smaller chamber was receiving the fluid only when it is getting drained/refilled.
By 200K miles, it said “enough is enough” and quit.
We installed transmission from the wrecked car having 50K miles of so, works great.
Now he changes his ATF every 30K miles like a clockwork :slight_smile:


To be fair, there’s no way of knowing if the trans would have lasted longer than 200k miles if the fluid had been changed regularly. I’m a proponent of changing the fluid myself, as I certainly don’t believe it hurts anything, and I have to think the friction modifiers and other additives degrade over time. However, I’ve had transmissions fail before 200k miles on a 30k mile change interval and I’ve seen transmissions last over 200k miles with no fluid changes. I’d be interested in seeing data (if it were available) showing trans longevity vs fluid and filter change interval. I do change the fluid as insurance. At least if the trans does fail, I can think “well, it wasn’t my fault!”

The problem with not changing the transmission fluid is that you don’t know if your transmission will make it to 200k miles if you neglect it. Sure, a particular transmission might be a lemon, and might fail at 95k miles, even with frequent fluid and filter changes, but that would be an outlier, not the norm.

Also, keeping the fluid changed is only one part of prolonging the transmission’s life. The other–more important–part is to drive gently and allow the car to accelerate gradually so the transmission can shift through all the gears in sequence. Don’t floor the accelerator each time the light turns green, that quickly wears out your transmission! And of course, don’t tow with your car if it isn’t specifically designed for that purpose, and equipped with a transmission fluid cooler.

I agree . . . might as well do fluid and filter services every 30K and hopefully improve the odds

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Fresh transmission fluid will have fresh seal conditioning chemicals. If only for that reason its a good idea to replace the fluid with a fresh batch. Auto Transmissions work under extremely high fluid pressures and therefore if the seals deteriorate enough to start leaking, the fluid pressure will drop, and all sorts of problems will eventually ensue. There’s no fundamental problem imo with using a fluid flushing machine to replace the fluid as long as it is done in conjunction with cleaning/inspecting the inside of the pan, and replacing the filter.

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Yup change it. I have not seen the Toyota factory manual but for both Honda and Nissan they are pretty emphatic to only do a drain and fill, and to do multiple ones if you want almost completely new transmission fluid. Its also an opportunity to go to a fully synthetic transmission fluid if you want to.