Toyota does NOT recommend that the transmission fluid be changed at a "regualr" service interval.
Change Automatic Transmission Fluid Only As Necessary.Generally, it is necessary to change automatic transmission fluid only if your vehicle is driven under one of the Special Operating Conditions:
You should perform these additional maintenance services if you drive primarily under any of the conditions noted. If you drive only occasionally under these conditions, it is not necessary to perform the additional services.Driving on Rough/Muddy or Snow-Melted Roads
Driving on Salt-Covered Roads
Driving on Unpaved or Dusty Roads
Extensive Idling or Low-Speed Driving for Long Distances
Towing a Trailer or Using a Camper or Car-Top Carrier
Off-Road Maintenance If you own a Land Cruiser or a four-wheel-drive RAV4, Sequoia, Tacoma, Tundra or 4Runner, you should check the following items daily whenever you drive off-road through deep sand, mud or water: