Auto trans fluid change

Best bet for changing the fluid in an automatic might be to buy a hand operated siphon pump and use it to "triple-change" the fluid when you do the filter and fluid change, because more than half the fluid stays in the torque converter even when you remove the pan. 

• Remove the pan, discard the fluid in the pan, clean the pan and change the filter. 
• Re-install the pan and fill to the proper level with new fluid.
• Drive the car for a few miles.
• Use a hand operated "siphon pump" to remove as much fluid as possible by way of the filler tube.
• Fill with new fluid to proper level and drive the car a few miles
• Repeat siphon-drive-refill steps once or twice more.

That should come close to completely renewing the fluid.