Here's how to change the automatic transmission fluid in a Toyota or Lexus with no dipstick.
Toyota claims the transmission in its modern cars is a sealed unit, and the fluid inside is good for the lifetime of the vehicle. However, transmission fluid does wear out overtime, and if you want to prolong the life of your transmission, its a good idea to change the fluid frequently.
The procedure for changing the fluid is more complex than a drain and refill through the dipstick hole that the old Toyota and Lexus models had. Instead, once the fluid is drained, a fluid pump must be used to pump new fluid back into the transmission through a fill hole on the side of the transmission, underneath the vehicle.
Since there is no dipstick, the transmission fluid has to be at a certain temperature when the fluid level is checked, and the vehicle level. This can be obtained using Toyota's techstream software, an advanced scanner, an inferred thermometer, or a special onboard diagnostic procedure. The overflow bolt is loosened and any access transmission fluid that is above its internal straw will drain out. Thus its a good idea to add a 1/4 quart more fluid when performing a fluid replacement.
Please note, this procedure will only replace 2.5 quarts of tranny fluid in most applications. The rest of the fluid, almost 12 quarts, is inside the transmission (mostly the torque converter). A full fluid exchange can be done by repeating this procedure 3 to 4 times, driving a few hundred kilometers in between. This will decrease the concentration of worn fluid in the transmission, but not completely flush it entirely, since the new and old fluids will mix.
Flushing the transmission through the cooler lines is not possible on this transmission type either, since the transmission does not have separate lines running to the radiator. Flushing the transmission fluid is not recommended for a vehicle that does not have transmission problems, even if the fluid has never been changed, and should only be used as a last resort before rebuilding the transmission.
World Standard WS Toyota genuine transmission fluid should only be used and can be bought from the Toyota or Lexus dealership.
This procedure is the same for most recent model Toyota and Lexus RWD and 4WD vehicles, including Lexus IS250, IS350, GS350, LS460, GX460, Toyota 4Runner, Tacoma, Tundra and Sequoia.
This procedure is similar to recent models Lexus and Toyota FWD and AWD models, with the exception that the transmission is mounted transversely, including the Lexus ES350, RX350, Toyota Avalon, Camry, Highlander, Sienna and Venza.
Here's a full DIY Write-up on the fluid change procedure for reference:
Its also a good idea to drop the pan and replace the filter, here's a write-up on that: