Instead of paying to have someone else do it, learn how to flush your auto transmission fluid in less than 10 minutes by following this tutorial. Unknown to most people, is the fact that draining your transmission from the bottom, only removes about half of the fluid, while the rest remains. This tutorial shows how to do a complete flush. First, find out how much transmission fluid your vehicle needs by reading the owner's manual. You will also find out what type of product you need to use. Reach underneath the transmission and open the drain plug. Place a pan underneath the drain plug and the oil will spew out. Allow that to drain. In the meantime, look at the drain plug and clean it off well removing all of the old metal shavings. After draining, screw the drain plug back in. Then, remove the transmission dip stick replacing it with a long funnel. Use this funnel to fill up the transmission with new fluid. Use an air hose to blow out all the old oil out of the transmission cooler.