I'm not sure about this, I was told that if you remove the transmission cooler lines and put the suction line in fresh trans fluid and the other in a 5 gallon pail you can change all the fluid in the trans. I was told change the filter and"o"ring with gasketfirst anyone ever done this?

 

Why tempt fate, your luck you would blow ATF all over the place when the pressure hits. It is not important to drain out every bit of fluid. If you do HD wheeling like I do then change the fluid every 15,000 to 20,000 miles.
Mike