Originally Posted by Beerfly
If you want the GFI to work and have 240 and 120 I am quite sure you will need 4 wires from your supply panel.
I don't think that's entirely true. I've seen many three prong dryers with internal lights and I don't think the lights run on 220v
There's just no individual "ground" instead neutral. When you have a four wire you ground to the dryer chassis. I think though that technically by today's standards they always want a ground for electrocution issues.