How do I open my differential on my mustang gt?

Ok, so i have an 04 mustang gt. And ive noticed that ive only been burning rubber on my left wheel and not on both. Mine doesnt have traction control, well the button between the defrost and fog lights. My friend has an 03 gt and he DOES have a the traction control and burn on both. So how can I open my differential, and if I do what will happen besides it being able to run on both wheels? Explain. Thanks!