For context: I have an older Toyota 05. 160k miles. Transmission fluid looks kinda brown and mechanic said I should do a flush and quoted me 300$. I’ve also heard that at some point you shouldn’t change the transmission fluid if it has t been changed in awhile. Why is this?
In: Engineering
It’s incorrect to say that you shouldn’t change it. The biggest concern is that changing it can stir up contaminants that then cause malfunctions as well as modify the fluid properties that can expose existing damage.
The correct thing to do is change it, but be prepared to conduct further repairs if you run into problems, including replacing it.
You can choose not to change it, which may prevent the sudden onset of related issues, but you *will* be condemning it to premature failure. Either way, be prepared to replace it. One option just has a chance of postponing the need to.
16,000 km is not an excessive interval for a modern transmission.
My mechanic said it depends on the transmission. Any regular car you should change the transmission filter forsure. If you drive a high end car, no need to change the fluid.
It’s not that replacing it, in and of itself, is bad. It’s the way that they sometimes replace it that causes the problem. A full flush is usually the culprit, it can dislodge gunk that might be sitting in a very old transmission with a lot of miles. If the fluid has never been replaced and the transmission has already seen a lot of wear and tear, that gunk might mess with some of the hydraulics of the transmission if it starts getting into places that it wasn’t in before.
There is a component at the bottom of the transmission called the “valve body,” which can be thought of as the “brain” of the transmission. It’s a hydraulic set of tubes, springs, solenoids, and valves, and is responsible for controlling the different clutch packs (the things that grip against the gears and engage them) with fluid pressure.
As you can probably imagine, it takes a lot of fluid pressure to make this work, and it has to be very finely tuned. If something starts leaking, or something starts to get clogged, or a spring, a valve, or a solenoid starts sticking, that transmission is going to start to act wonky.
It’s really only on very old vehicles that you have to worry about this. Something has to go terribly wrong for a fluid replacement to cause a transmission to fail, in most cases the transmission was already on its way out. A lot of people recommend doing a drain-and-refill rather than a full flush on older vehicles, as it’s less risky in terms of potentially dislodging anything that might be in the transmission.
This video is a great summary of Toyota specific transmission maintenance. Very easy and simple to digest. Highly recommend the rest of his channel if you’re interested.
I did our 2012 Sienna trans fluid and filter. It has an insane way of accessing the fluid and checking the level. I think the 05 has a dipstick so should be MUCH easier.
I feel like newer transmissions are sealed and don’t need the fluid changed or anything unless problems start happening.
I think I read that somewhere…
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