Correct me if I'm wrong, but I don't see anywhere if you had the same problem before changing blades. Is this truck new to you? Did you have the same problem before? I would find it very difficult to believe that it is your windshield. How long have you owned the truck?

 

Also, if your wipers work fine at a stop, or below your 40mph threshold, it can't be your windshield. You are experiencing wind lift.

 

I didn't have this problem that I noticed before I changed the blades, but I only drove in the rain a time or two before replacing them. I've had the truck 4-5 months.