May not be the blades...just might be the windshield itself. Windshields pick up all sorts of garbage from the air; if water beads on your windshield it's contaminated and your blades may chatter. There used to be a terrific product put out by the No-Touch people named "Windshield Stripper" It removed everything from the window glasses and eliminated streaking and chattering. When Permatex bought No-Touch, Inc they discontinued the product. Now the best you can do is Mother's or Meguiar's "Water Spot Remover"...used only as directed. Oh...Rain-X was developed for use on the acrylic windshields of aircraft; don't use it on glass unless you want water spots and chattering.