Okay, sorry but just remembered that persistent wiper chattering can be caused by blade-to-windshield angle which is pretty straightforward to correct. You'll need an adjustable wrench long enough to provide torque to twist the end of the wiper arm (about 6") and another to support and hold the end of the wiper arm where it emerges from the base. Slide the wrench at the end closest to the wiper blade over the arm and adjust to the thickness of the arm. Do the same for the other wrench at the base. Simply twist the arm at the wiper end slightly to change the angle of the blade to the glass. If the blade is chattering on the up-stroke, make a slight change to angle the wiper edge down. Experiment with small changes to get the best results.