"Bitsbucket" news: snipped-for-privacy@free.teranews.com :
This is how it works:
Make sure you take it to an oil change place that has a sucking machine....what happens is that most cheap places and dealerhips is that they drop the tranny cover, charge you for an uneeded new gasket and that bottom pan magnat thingy, which you don't need and then button it up again, many times it leaks from shoddy installation of gaskets, usually overfill it with oil and send you on your way $150 poorer.
This is horrible.
Because what should be done is to have it sucked out by a specific machine. See, the torque converter has about a quart of fluid in it that won't come out when those bastards just drop the pan. The sucking machine works like a dialysis machine; one tube in and one tube out. They run clear clean fresh flud until the exit fluid also runs bright red and clear. That way you know you've got all the old fluid flushed out.
$79 at most oil change shops.
Next, additives:
Yes, they do work...the reason is that internal rubber parts and gaskets become old and brittle and they need chemical additives to keep them soft and pliable. Old tranny fluid has had most of those chemicals burned or evaporated off. Failure of internal soft parts is the main cause of tranny failures.
HTH