I did a full ATF fluid exchange at 81k on my 2014 as preventative maintenance. I bought 13 quarts of the Toyota WS fluid but used close to 12 quarts. I also dropped my transmission oil pan to clean it, along with the magnets and filter screen. Replaced the pan gasket with a new one from Toyota, torqued all the bolts back to factory specs. Original fluid drained with dark brown.

My driving consists of many miles on 4HI/LOW while on trails, plus hauling heavy camping gear back and forth over the mountain passes here in the PNW. Now I'm at 95k and no issues at all since the fluid exchange. Transmission shifts just as smooth as when the vehicle was new. I've added a Hayden 678 tranny cooler which as been keeping the operating temps down by nearly 20°. Next exchange will be another 80k+.