Grease a 9x13 pan and preheat the oven to 350 degrees F.
MAKE GRAHAM CRACKER CRUST:
Whisk together graham crackers, melted butter, and ⅓ cup granulated sugar in a medium mixing bowl.
Gently press the graham cracker crumble evenly into the prepared baking dish and bake for 8 minutes. Remove from the oven and allow to cool completely before continuing to the next step.
MAKE CREAM CHEESE LAYER:
In a stand mixer fitted with a paddle attachment, beat the cream cheese on medium-high speed until smooth and creamy, about 1-2 minutes. Add remaining ⅓ cup of sugar and mix until combined.
Fold one package of thawed cool whip into the cream cheese mixture using a rubber spatula.
Spread the cream cheese mixture over top of the graham cracker crust.
MAKE PUMPKIN PUDDING LAYER:
In a large mixing bowl, combine the pudding packages and milk, following the pudding box instructions.
Add the pudding over the cream cheese layer and carefully smooth it into an even layer.
COOL WHIP LAYER:
Layer the remaining 2 packages of cool whip over the top of the pudding layer.
Sprinkle the toasted pecan pieces over top.
CHILL, SLICE, AND SERVE:
Cover and chill in the refrigerator for 8 hours or overnight before slicing and serving.