The total capacity of the 8HP is around 9 liters. When I did my transmission service, including the pan, it took almost all of the 6 liters. If I can drain almost 6 liters from the pan sucking out 2 is not an issue. When you start the engine after filling the pan it is already low on fluid.
I did this twice already and if I sucked the pan dry and the intake would have been sucking air I would know it by now.

Sorry, I edited my earlier posts after I checked my notes, it was 2 liters I sucked out not 3.

I have the 8HP transmission with a pan that has the integrated filter.

https://blog.fcpeuro.com/how-to-chan...d-transmission