... How many miles do you currently have? And if you DID lose your transmission, how many miles did it have when it died? No judgement from me; I'm just trying to find out about when they might die if their ATF was never drained and filled.

--edit-- I guess ANY mileage that anyone has on their 4th gen with ATF never changed, please post that. All these 4th gens have got decent mileage by now.

I guess the replies you get will depend on what you consider high mileage.

So I had a 03 where the transmission went out at 150k. The issue though was related to the transmission cooler failing, which I believe Toyota improved in the 06 updates

I just drained and filled my 08 at 165k as the hard lines from the cooler had rusted through and the fluid looked really clean. It may be a coincidence, but since then, the truck is downshifting a lot more rough

I guess any mileage that anyone has on theirs that never had its ATF changed. All these 4th gens have got decent mileage on them by now. It would be really good to know if a lot of these "lifetime fluid" transmissions start failing at 200k or 300k or 400k or when. There are a lot of used ones on the market, and a lot of them don't have records of whether or not the ATF was ever changed, so it would be good to know just how long they will last if the fluid was never changed, balanced against the choice of whether or not to risk changing it for the first time at high mileage. Maybe I could have worded the question better. Looks like I can't change the title, but I'll edit the post. There are people out there draining and filling their ATF every 30k, and there are many who never have.

Changed mine at 160k.

Followed this DIY: ATF Exchange (using the cooling line)

I'll be exchanging every 100k.

Thanks. Did you notice any difference in the way it shifted?

Not really. Oil was dark and in need of a change though. Glad I did it.

I bought my 2007 with 220,000 miles. Did a full fluid exchange with Amsoil and it made a big improvement in shifting. I now have 232,000 and still shifting like a new truck. Im pretty sure the fluid had never been changed before that. But I do go the extra step and add a Magnefine inline filter to the cooler line. New fluid will dislodge old crud and the filter will keep it from recirculating. Its $25 and gives me peace of mind.

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IMO changing trans fluid is part of periodic maintenance, regardless of what manufacturer says, whether at 30, or 60K miles, do it. I do a pan drain and refill about every 15K miles or so.

I have 146,000, '04 V8, no trans oil change yet.

When you think about a drain and fill, you only change 2 qts of a 12qts system. What are you really helping to replace just 17% of the fluid? Do it again in a week/month and its now diluted with the old fluid and its probably only 20% new fluid. One, it will get expensive quick that way, two, its not helping the tranny at all. Third, if you are under the truck doing all the hard work getting dirty, just change it all and be done with it for another 100k miles.

Agree - generally with a drain and fill youre only getting the fluid in the transmission and not in circulation and its only a portion of it - It may be more like 3-4 quarts of 11. That said, I lost a lot more of mine when the cooler hard lines rusted through and I replaced the radiator. I was surprised how clean/ red/ kool aid appearing mine was

When I drain my trans pan on my '03 V8 I get almost 4Qs out. Same on my '07 Highlander, I did 3 drain and refills on it after a couple of drive sessions in between, a couple of years ago as it had been a while.