If you have cracks in your pumpkin pie, you might be over-baking it. My favorite tip? Pull your pie from the oven when the pumpkin filling has domed edges and a slightly wobbly (not sloshy or liquid) 4- to 5-inch circular center. Check out the pic below, so you can sort of see what I mean.
Your pie will finish setting on the counter with its residual heat. Once completely cooled, your pie will be smooth, cooked through, and free of cracks!