I am the fresh owner of velfire and about to go for trasn flyid change . I am aware book says something like 6.5 litres but we all know that torque converter does holds some and lucky if i do drain half .

Now is the question someone that did it 

Howany litres should i buy ot top of the strainer and if the gasket does survive? 

As the gearbox is the same on the Camry, I followed this video (and mixed it with a bunch of others) : 

 

I followed the Toyota technician software too, and ask a friend of mine who's Toyota mechanic how they do the flush on this type of transmission.

In resume, for me the most important is : 
- Take a graduated container to have an idea of how much you got

- Don't forget to remove the overflow tube when flushing
- Replace the filter

- Don't forget to put in back the overflow tube

- Overfill a bit
- Use a laptop with Techstream to get the fluid temperature, then you'll be able to make the level accurately.

Bit pointless as i know my trade just the fact that i was after amount of fluid that drains on replacement 🙃