There is no such thing if you have a second gen explorer. Because you have a 96, you basically have them in the form of your central axle disconnect "CAD". The axle shaft on the right side is actually two pieces and when you shift into 4wd a shift fork on the axle moves a coupler to connect your two axle shafts together. Or you could do what I did and put in a Manual shift BW 1354 and then permently lock the CAD. This provides a much better 4wd system than the Auto 4wd that only turns on after you are nice and stuck.