You can type in Google and said every 30,000 miles, but I drove 40,000 it is shifting normal, I also drive normally most of the time and it you change after extra 10,000 to 20,000 thousand miles, U would be extending 4-5 years, providing every time you change U put new fluid and new gasket including transmission drain plug paper gasket just like oil. You should feel how your Sienna gear shifting between 30,000-50,000-mile n decide when 2 change. I suggest U buy OEM filter gasket from Toyota dealer, still cheaper, so that it can fit perfectly and OEM fluid, nothing can go wrong 4 next minimum 3 to 5 years is worth paying any shop with auto tech *shoulder patch that has *ASE logo* on it*, they are confident auto tech proven academic knowledge in most cases, always exception in everything and make their job so much easier and less charge since you are supplying OEM parts that fit perfectly! Try 2 help!
@@gumerasgarage5328 By only changing fluid if there is some kind of the build up (but you don't know because you did not look in the pan) the new fluid has detergents that will loosen this build up and clog the filter which would make it worst.
Im not saying that you're wrong. All im saying is that in case you just want to change your trans. fluid, this is how i do it. But in my next video, "How to change trans. Filter, " i will show what you just mentioned. Thanks for your input