Too clarify changing rear diff. on a v6...
Automatic no additive needed
Manual-additive needed
Like rtcat600man said...after the car is jacked up, take out the top bolt first and clean off the plug...make sure you keep the o-ring if it falls off when you take it out.
Next, put a pan under the bottom plug and take out that plug. (BEWARE use gloves!!!! This fluid is nasty smelling and it is difficult to get rid of). Again, clean that plug.
Some people move their jack up and down to get every last drop. I didn't find this necessary so I just put the bottom plug in. It is a little tricky getting the fluid bottle to fit correctly to fill the the top plug. You may have to squeeze the bottle and move it around to get it to go in. Then put the top plug back in.
After you have the plugs in, take if into a parking lot and do some figure 8's to get the fluid moving around the gears.
http://www.camaro5.com/forums/showthread.php?t=161654
This is the thread I went by when I changed mine.