ATF flush or drain re-visited for a specific application.

Question

In reading the comments posted here, I understand that the majority of you recommend that the automatic transmission fluid does not need to be flushed, but simply drained and filled. But I would like to address my particular situation. I realize that I will probably be directed to view FAQ's, but I have done that. I purchased my 2004 Avalon with 40,000 miles in "like almost new" condition as a certified pre-owned vehicle from a Toyota Dealership. They recommended to have the ATF flushed every 30,000 miles. I was informed that for this car, they did not perform drain and fill, but rather flushing as that is the only way to clean out the old fluid from the differential. It made sense to me, so that what I have done ever since. Now at 162,000 I have never had any problems with the transmission. It shifts as smoothly now as at 40,000. I plan to keep this car. I have had regular 5,000 mile oil and filter changes at Toyota and I change the air filter every 10.000. The car does not consume/burn engine oil nor does it leak any fluids. Recent Akebono brake pads and Michelin tires all four plus I replaced the headlight assembly with aftermarket as resurfacing them was tiresome and never fully clear. So back to the ATF. I understand that dry fill holds 8 quarts and when draining only 4.5 is emptied leaving approximately 3.5 quarts inside. To me that is like draining 3.9 quarts of motor oil and leaving 1.1 inside if it were possible to drain all 5 quarts. If the ATF flush and fill method has been effective, is there a logical reason to switch to drain and fill. Perhaps I am missing something or not as knowledgeable as some of you regarding a higher mileage automatic transmission.  Thank you.

kesterpaul62 · Accepted Answer

Posted by: @avalon04 Toyota Dealership. They recommended to have the ATF flushed every 30,000 miles. I was informed that for this car, they did not perform drain and fill, but rather flushing as that is the only way to clean out the old fluid from the differential That is a whole bunch of nonsense that dealers will tell you. Just do a drain and refill on your transmission.

MountainManJoe · Answer

Posted by: @avalon04 that what I have done ever since. Now at 162,000 I have never had any problems If you replace the fluid regularly, the transmission doesn't experience extreme conditions, and it's done by competent people, then the fluid exchange itself shouldn't cause a problem. The problems arise when a transmission is neglected for a long time, abused, or the job is done half-ass. Unfortunately, this is the case for too many so called "mechanics" out there, especially the halfwits at quick-lube joints. For example, we had one visitor here who had a transmission fluid exchange done, and some time later the transmission hose blew off and ruined it. The other issue is that there are many different kinds of "flush". Some simply exchange the fluid which are pretty safe, but some add pressure to the system, and some even use chemicals. You never really know what you're getting, and who knows what else they'll come up with or what other shortcuts they will take. Because of this uncertainty, and risk compared to the benefits (which are few or non-existent), both I and Scotty condemn flushes in most cases. In cases of contamination then a flush may be the best course of action Posted by: @avalon04 I understand that dry fill holds 8 quarts and when draining only 4.5 In most cases, that's good enough, and has been for decades. I know the dealerships and some shops will give you a whole song and dance about not replacing 100% of the fluid (which is impossible by the way, even with a flush, as a lot of the fluid is bypassed). But the truth is they love flushing because (1) it's quicker so they can save labour time and (2) they can charge you more money for it, which leads to (3) a lot more profit for them.