When I see "ATF", I think of the Alcohol Tobacco Firearm agency. Only cause I had a small file with them cause we did alot of dry ice bombs in high school. We never hurt anyone though, always did them in big fields.
drain the old fluid and put new fluid but put an extra qt or so, then under the truck there will be 2 small lines going in and out of the radiator those are your trans fluid cooler lines take both of em out and put it in a bucket and start the truck then when the fluid turns red turn off the truck put the lines back run the truck and put it into gear then pull the stick.
my truck stayed in gear in the drift vid? Most people assume my truck is manual, its pretty funny. I want a manual though