Makes sense, thanks.

But then could one not just drain the fluid, drop the pan and shouldn't all those deposits be attached to the magnets?

I suppose after doing that you've basically flushed the system, no?

Pan drain does not get the majority of the fluid - the torque converter has a lot in it.
Some of the material floating around in the oil (clutch plate, etc) is not magnetic and whiz right by any magnets that may be on duty.

History shows this transmission to be very robust and long lasting.

That being the case, the first question I ask myself is what could screw that up. That means never touching the fluid at all is one option. I use my truck pretty hard, though, and am not quite comfortable with that one. The next most conservative approach is drain and fill which is what I've done. I see no need, especially with this transmission, to risk a flush.

not really. i did a complete flush. i removed the pan, cleaned the filter and pan, reinstalled it, fill it up, disconnected the hose on top ofthe radiator, directed it to a container, started the car until the just half way full, added more fluid, and did this a couple of time until a reddish color is starting to show. i used up around 16qts for this.

make sure to measure how much oil you removed from the pan and refill it the same amount.

Here's a more detailed instruction.
1. find a 1 gallon milk container. measure and mark the 1st qt to 4th qt.
2. drain the pan and remove the pan and clean both pan and filter.
3. measure the atf you drained using the milk container. (need this later when refilling).
4. reinstall the clean filter and pan (use new gasket and torque to specs)
5. disconnect the atf line from top of radiator (driver side) - find out which one is the return line and line from pump.
6. get a hose (clear hose) that will fit inside the hose coming from the pump (seal it with teflon tape, then direct it to the milk jug all the way to the ground.
7. connect another hose to the fitting in the radiator and use it to fill the transmission with oil. (only use the amount of oil that you drained out from step 2) - this may take a bit longer unless you put pressure
8. once refilled, start engine and watch the milk jug until it's filled up to 2 qts and stop the engine.
9. refill it with atf again with another 2 qts and proceed with step 8. continue until a reddish color appear on the hose and don't do step 8 anymore.
10. remove the vinyl tubing and reconnect the hose to the radiator and the clamp.
11. YOU FINALLY FLUSHED YOUR TRANSMISSION. NOW IS THE TIME TO TEST DRIVE IT.

Just drain and refill. Maybe a few months later drain and refill again. This will allow you to get much of the old fluid out.

Soooooo ...

Just curious. All you folks doing these fluid changes at home, what are you doing with the old fluids? I'm reading of up to 4 gallons of ATF needing to be disposed of in some cases.

I do all my own oil changes because I can take all my waste oil to the recycling center but I know of no place where I can take ATF or other vehicle waste fluids without paying $$$'s in disposal fees.

What are you guys doing? (not sure I want to know)

most dealerships should take the other fluids as well.

The recycling center out here takes it all, petroleum based or not, if you're a customer and bring it in yourself. There are volume limits but they're pretty generous.

FYI all Jiffy Lube locations will take any motor vehicle fluid except gasoline/diesel fuel.

I have dropped off used motor oil, gear oil, ATF, P/S and brake fluid. Every time they have even come out to my truck and taken away for me (I have the jugs of used stuff boxed up).

How would they flush it if it's sealed? Do they take the whole panel off? Like on older model cars, truck you have a entrance port for transmission fluid and an exit plug like for oil. I have not seen things. I don't tow that much. I once towed a 5000lb excavator and a trailer with a bike at one point also 2000lb of cement mix twice. But over all 95% of the time I owned the Runner it's been a mix of highway and regular road driving.

Flushing is usually done from the tranny cooler lines. Also "Sealed" doesn't really mean sealed. There are drain and fill holes/bolts/port just no dip stick.

Great to know ! Is this true even if you don't have any work done there ?

Toyota specifically states to do a Drain & Refill, not a flush on any of our "sealed" transmission as do the manufacturer's of the flush machinery.

There is a drain & "level indicator port" on the bottom of the transmission, you drain the fluid out and them pump in WS Fluid usually by a hand pump like you would a manual trans or differential. Then you bring the trans to a specific operating temperature and check the drip tube for fluid flow... Its pointlessly over complicated, but there is a procedure and many members have posted the information before.

don't flush its not recommended by toyota! If you do 4 drain and fills with 500mile intervals using the toyota ws fluid you will be perfect! Read the manual it states only to use toyota ws fluid. Here is the process for the tacoma, its prob the same for t4r. can a toyota tech verify.

How to Drain/Refill Automatic Transmission - Tacoma World Forums


2018 Edit: I used the Timmy the tool man method Transmission fluid flush