Just saved myself $100. The rear wiper motor was acting up- not returning to its park position. Removed the motor but saw the cover on the gearbox was not removable. The cover is held in place by five "studs" flattened on the top, kind of like a rivet. I figured I'd have to replace the whole thing. When I found out a new one is $220 (in Canada) and even a used one would cost me $100, I decided to try and fix mine. I ground off the heads of the little studs and the cover came off easily. The large gear inside has three contacts that ride on metal tracks- this is how the motor returns to the park position. The grease inside had hardened up to the point that the contacts were only able to touch the tracks intermittently. I cleaned off the grease, polished the contacts and tracks with emery cloth and put some new grease on the worm gear. I ground off the remnants of each stud on the body of the gearbox then drilled holes through where the studs had been, threaded the holes with a 4-40 tap and put the cover back on with five 4-40 screws. To my delight IT WORKED!