You can get very close to 100% of the fluid out of an automatic as long as it has an external cooler. This is also how a transmission fluid exchange machine works at a shop.
viewtopic.php?f=28&t=3656
Prowler's method (post #2) has been used and tested for years now, but both that and the original method will work.
Taking it to a shop can be dangerous if you do not know which method they use. Some will use chemical flushes which are not always compatible with transmission seals, and some will do a reverse pressure flush to get around cleaning the filter (bad!). Older, neglected transmissions can even suffer from a forward pressure flush, but in many of those cases the transmission was failing to begin with (I still would avoid all but a "fluid exchange" machine that uses the transmission's own pump).
viewtopic.php?f=28&t=3656
Prowler's method (post #2) has been used and tested for years now, but both that and the original method will work.
Taking it to a shop can be dangerous if you do not know which method they use. Some will use chemical flushes which are not always compatible with transmission seals, and some will do a reverse pressure flush to get around cleaning the filter (bad!). Older, neglected transmissions can even suffer from a forward pressure flush, but in many of those cases the transmission was failing to begin with (I still would avoid all but a "fluid exchange" machine that uses the transmission's own pump).
