2005, 4.0, 298k.

Just did my in drain and fill and then I exchanged all the fluid using the cooler line up front, but I filled at the drain plug with a funnel and a long clear tube, looking down on the passenger side along the exhaust into the fill plug, plastic spring clipped the tube to the exhaust shied near the fill hole to secure it.

Fitting at top of radiator for transmission cooler is 3/8. Here was what I used, probably in plumbing supply at most retailers that sell plumbing supplies(Menard's here);

Here's my connection, black rubber tube going into the radiator will be the fluid that is pumped from the transmission;
3/8 inner diameter clear tubing, 3 feet
3/8 to 3/8 connector
Drain jug with 2qt and 4 qt levels marked
plastic spring clip (tube at jug)

Funnel set-up to fill from above (I've never used a pump);
Flo tool flex funnel(Walmart) + Less that 3 feet of 1/2 inch inner diameter clear tubing(Menard's)
plastic spring clip (tube by fill hole)
Fill plug is 24mm, (if possible use breaker bar to loosen, or long wrench(knuckle buster...))

3 gallons Valvoline Maxlife (bought 4, one for stock being I didn't use it)

My method, learned from Sienna guy, add 1 extra quart, run the motor, drain 2 quarts, add 2, till the last time then just add 1 qt.
Time at 5:40 for fluid exchange, (ignore his jug on the topside, it's where you'd fill at, but he has a dipstick tube)
2009 Toyota Sienna Transmission Fluid Flush and Filter Change
YouTube


more details (I was going to keep this short...);

I must have started with the flex funnel somehow connected to 3/8 tubing going into the radiator, you should do this at first to clear the fluid out of the cooler if you use the top line in. Use any small funnel that connects to 3/8 tubing. The filling at the top cooler line (driver side) of the radiator goes so slow, you'll want to fill through the fill hole at the transmission, first I wanted to use the lower radiator line out, but it added difficulty and I wanted simple.

Initially, I left the drain plug off and just let 1/3 qt clean fluid chase down through the cooler (radiator) and drip out the pan to clear that part. I took the funnel off the clear tube and blew into the tube it was going so slow, that's when I opened the fill plug. To summarize, ran 1/3 qt through cooler, installed drain plug after it started to drip real slow.

Preferably get a new drain plug and gasket, and if the old plug is good keep it for a spare, mine is not perfect (next drain and fill will be replaced).

I used 11 and 3/4 quarts Valvoline Maxlife ATF. I open the transmission cooler line at the radiator I think I got maybe 7/10 of a quart out through the transmission cooler, measured after I drained the pan. I'm not sure of the total capacity, I thought 11 qts, somewhere in this thread I read 13 qts. Mine was noticeably red, as I saved before/after samples to show my buddies.

Change your fluid, I'd say at 30k to 40k it's gonna be dirty. Even if you're beyond whatever miles, because of the clutch plates and the friction material that wears off and you don't want that running through your solenoids clogging them up. It's basically a hydraulic machine, and Toyota transmissions are resilient from my experience.

Just adding dropped the pan and changed the filter last year, that's why I didn't get into that here.

If I haven't convinced you, try this;
Bob Is The Oil Guy
ATF, Differential, Trans, Brakes, P/S
ATF, Differential, Trans, Brakes, P/S - Bob Is The Oil Guy