anyway backdoor ways to change transmission fluid at home on this sealed unit

Leave the car alone!!! WTH!

I agree leave it alone at present, but when you may need the trans fluid changed check owners manual to make sure you use the correct trans fluid, some vehicle manufacturers require you to use the car makers trans fluid, and also if you use a dealership check and see if they offer discount coupons for trans and other services, if not try another dealership.

I have to disagree with the other responses. Toyota wants you to have low cost of ownership for 100k miles. If they have recommendations to change the fluids before the 100k mark it ups the calculation for that figure. Toyota wants to sell you another car at 100k, not help you to maintain the car for 200k plus miles. I would suggest changing the transmission fluid at 50k, depending on how the vehicle is being used. Change your fluids and keep the car longer, it's a better financial deal in the long run.

DO NOT TRY THIS AT HOME --- I did and it just cost me $415.21 to have my system flushed and refilled by a Toyota dealer. I drained the closed system and filled with the 6.9 quarts of Toyota special transmission fluid prescribed ($9.75 per quart). It took that much for the fluid to get to the top of the fill port as noted on U-tube videos. I drove the car at Interstate speeds for about 60 miles when the Check Engine and the Slip Indicator lights illuminated. I drove on for thirty more miles (not recommended but necessary) and when I stopped, smoke drifted out from under the hood -- it was transmission fluid which was covering the outside of the transmission and burning. Today, I took the car to the dealer (the lights were not illuminated because the engine/transmission had cooled). This is NOT your father's transmission!! The dealer corrected the situation (took 2 hours) and fortunately I had not done any permanent damage. The dealer has a special machine insert the fluid from the BOTTOM of the transmission. He then follows a process of running the engine and adding fluid until the correct operating temperature is stabilized. Unless you want to buy the special equipment and become a dealer, LEAVE THE TRANSMISSION ALONE for 100,000 miles and then pay the $240.00 for a flush and fill. That is a about the same cost as changing the fluid yourself every 25,000 miles and a whole lot cheaper than a new transmission!!

JackGas - your experience seems strange... draining the system resulted in 6.9 quarts which you used as your metric with filling it back with 6.9 quarts of new fluid? I find it hard to believe you got 7 quarts out just by draining it. Seems like an awful lot. You do not need all that special equipment UNLESS you are filling it at a temperature that is higher than 104-113 degrees Fahrenheit that the included straw/tube was designed for. You mentioned fill port as well. That is the bolt on the side that is used to fill with fluid and if you filled it to the level where it started coming out of that hole you definitely did it wrong in the first place!