For anyone looking to do a full flush on a 4r70w transmission, here's notes on how to do that:
I'll add 2 things, see his added note at the bottom, pump the pan empty before you take it off, it makes it a much less messy job.
Also if your car is earlier than 2002 (and some early 2002 ones) you will have a drain plug in your torque converter. After pumping the pan empty, take the rubber plug out of the bottom of the converter cover and use a wrench on the crankshaft bolt to turn it clockwise until the converter drain plug is right over the hole in the cover and drain it.
Its no big deal if you don't have this drain plug, it just means you need to pump more clean fluid through to get the flush done. I don't have a plug and put 14 quarts of new fluid through mine to get it really flushed out well. Amazon.com has pretty good deals on ATF 6 packs, my local auto stores wanted twice as much.