Lots of rain last week, after a dry, dry summer. Noticed that the wipers became very erratic in where they reversed their stroke. Would start working fine, then after a few minutes would start slapping at the bottom of the stroke, and the right wiper would sometimes come way over at the top of the stroke. Wind at highway speed seemed to move them around a lot. Motor? Transmission? I'm guessing the guts are under the plastic vent thingy at the bottom of the windshield. How tough to get at?