Many Whirlpool fridge models so I'm sure there are various ways. The Whirlpool Gold we have at home has a lower basket that lifts out of the main drawer, but the top sliding basket does not come out without disassembling the upper part of the slider mechanism. It's a real PITA if I have to clean the interior.
On some Whirlpools, you actually remove the face of the lower drawer (loosen 4 screws and lift it off), which then give more access and the ability to remove the slider rails and upper track for the top basket.
If you enter your Whirlpool model number on an appliance parts site, you can probably view an part diagram of it. Here's one site:
http://www.appliancepartspros.com/whirlpool-parts.html