Transmission Drain and fill on 2016 Tundra with 125k miles?

I want to do a drain and fill on mine. I did one on my old GX.

I just measured what came out, and measured how much I put in, and added just a small smidge to account for fluid left in hose, etc.

My question is more about this particular year. The GX I did only had two bolts, drain and fill. These have three.

So my question is, is the third bolt basically like the fill hole on the differential? Meaning if during the fill I also removed that bolt and filled it until fluid dropped out of the third bolt, would that not mark the right amount of fluid?

 

Kind of, but not really. The second plug on the bottom of the pan is the level check plug. There is a procedure to follow, but basically after draining and refilling, you get the transmission up to ~110F, open up the level check plug with the vehicle running, and observe the fluid that comes out for a trickle - not a drip, not a stream or a deluge, a trickle.. Make sure the truck is level. The drain plus is 14mm IRRC, the check plug is 5mm hex key.

 

https://youtu.be/NUAuGmDGntY

 

Drain plug is 14mm

 

Ummm... that's what I said...