I have a 2003 V8 4Runner (with trans fluid dipstick) with approx 160k miles. I haven't had the vehicle too long and so am uncertain as to the history of ATF changes. However, the fluid on the dipstick does look nice and pink/red in color. I am looking to change the fluid, however, am getting some varying advice on what should be done. I have read/heard that in general it is not a good idea to replace all your transmission fluid (eg. a full flush) if you are uncertain how regularly it has been changed. I believe the reasoning here is that replacing all the fluid with new more viscous fluid could cause problems or perhaps the flushing action could dislodge shavings etc. My Toyota dealer offers either a full flush (with some sort of machine) or a drain/fill. They recommend the full flush in order to ensure all fluid is the right stuff and they haven't really heard of the flush concerns that I mentioned. I decided to call another dealer and their service guy said given age etc of vehicle, he would not recommend a full flush (saying something for example about could dislodge something unwanted from torque converter). He recommends drain/fill but also says that would replace about 80% of the fluid (I didn't think a drain/fill would replace so much). A couple other calls got me yet more mixed messaging about whether a full flush is appropriate. And another that says to pull pan and replace filter?

What are the experts on this forum doing in similar situations? On one hand a full flush would ensure you get all fluid replaced with the right stuff (who knows what is in there now even though it looks ok), however, I wouldn't want to compromise the transmission in any way.

Ideally, a flush shouldn't damage anything/act much more differently than a drain and fill if you go by this method.

Easy Peasy transmission fluid exchange V6

That being said, I would go slow, 2 or 3 quarts maximum at a time.
When I last had mine done, it was drain and fill, and my truck is fine. Next time (maybe this winter) I'm going to use the above method.

A pressurized fluid flush is something you will likely want to avoid. What you want is a fluid exchange.

ATF Exchange (using the cooling line)


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Don't bother following either of those threads for draining and filling the ATF in your 2003 V8. There is no need with the 2003 V8 since it has a drain plug on the trans pan and you fill thru the dip stick. Ask me how I know.

Drain fluid from the trans pan via the drain plug. Refill via the dipstick tube. Then go for a drive to warm up the ATF. Park and check fluid level via the dipstick with the motor running, trans in Park. Add fluid if required to bring it into the HOT range. Done.

Highly recommend the Valvoline MaxLife ATF that is mentioned in those threads otherwise. It's good stuff.

Edit: My mistake, I was looking at the manuals and was seeing 2 plugs but just looked underneath my 03 and there is only one, the drain plug, at the back of the pan.

So drain via the drain plug, reinstall said plug, refill via the dipstick tube to cold level, drive to warm up and check/fill as needed with trans hot and in park. Level should be in the HOT range on the dipstick.

At 160k, you would probably be safe doing a flush but there really isn't a need for it. I would recommend just the drain/fill. There are replacement filter available, which does involve dropping the pan. That's up to you if you want that done or not. There is a possibility of the pan leaking if the mechanic isn't careful about straightening the pan before reinstalling or if a gasket is used. Toyota pans don't use gaskets, they use FIPG (fancy Toyota RTV).

I'm a fan of the drain and fill...seems like the "safest" and easiest option, especially given that you have a dipstick. Drain out and measure fluid, add the same amount back in, drive and double check. Done. Repeat a couple hundred miles later, and don't sweat it.

Thank you for the great info. With the drain (from the plug) and refill (via dipstick) can I expect to get much out? One of the toyota techs i spoke to seemed to indicated you would get 80% out - I kinda doubted that. I thought maybe you would get 25-30%. So maybe do a few times over a period of time.

80% is probably pretty close honestly. It doesn't account for what's in the lines and cooler, not what's in the torque converter. So 80% isn't bad at all.

Depending on how hard you drive and the conditions, you could shoot for a regular 30k mile change interval. Do the drain and fill now, assuming about 80% or so fluid changed. Give it 15k and then change it again. From there, just do 30k intervals and call it good. That's my plan at least. Got about 5k more to go before I change it again and go to 30k intervals.

Thanks. Do you normally replace the drain plug washer/gasket each time as well?

Does the 2003 V8 4Runner (with trans fluid dipstick) Has a 340 4 speed or the 750 5 speed?

It is 5spd transmission.

thanks Jay

i agree with the above posts that say to do a drain & fill to keep it easy, then another 1 or 2 after a few hundred miles. however, you can still do a full exchange via pumping fluid out the trans cooler line port on the bottom of the radiator ~2qts at a time, you start the engine for about 10-15 seconds with a line into a marked drain bucket, then refill the same amount via the tube. do that 5-6 times & youve done a 90-100% exchange. i also recommend the valvoline max life fluid, especially on T-IV fluid but WS too.

& draining the pan does not replace 80% of the fluid, the trans & converter hold ~12qts, the pan holds about 3, that is 25%, not anywhere near 80% of the total fluid. so a few drain & fills are needed to replace most the fluid.

you trans with a dipstick makes it very easy to do either a drain & fill or full exchange. i would avoid a machine power flush.

ive done a 3x drain and fill on 2005 camry (dipstick avalable) and a 4x drain and fill on 2013 camry (no dipstick available, pia process to measure fluid with internal drain plug in the transmission pan).

boght a 2ft socket extension to make the non dipstick models easier next time, to avoid dropping the wheel to access the fill plug in the wheel well.

i have not done this on 4R yet, but when i get to it..its on the list to get done.

if unsure, i would go with the drain and fill.

performing this process several times.. you will also get to know your 4R pretty well and will make oil changes seem really simple..lol.

i went with toyota oem ATF fluids for each model and plan on the same OEM fluids for the 4R

potential ideal maintenance schedule, im pondering is performing a 1x drain and fill on the non dipstick models annually during an oil change, to keep the ATF in good condition perpetually..but that probably turn into a every other year schedule.

No, doing the fluid exchange via the cooler port is so ridiculously slow, it's not worth the time and effort. I tried it on my 2003 and it took like 6 hours to do. Just stupid. The simple drain and fill for the 2003 is really the best way to do it. If it really is only 25-30%, then I'd just do it 3 or 4 times with the drain and fill method. I'm not going to waste my time with the cooler line again.