icanfixall
Official GMM hand model
The hood cowl drains are on each side of the truck. Look down under the rear edge of the front tires. You will find a black mud flat looking piece of material. Reach up behind that and the floor of the cab. There is a rubber one way valve thats about 3 inches across. Just squeeze it open and dirt or leaves might drop out. If the cowl vent is loaded with water first it will kinda wash out the pluggage but..... It will get nasty and you are going to get wet.... I removed both of my inside the cab kick panels at the floor... Then dug out plenty of muck.... Only then did I find an easier way to clean this out...