I lost the washers on my car last year, on investigating I found the wiper drive arm had been rubbing on the washer piping, rubbing through it and causing a leak. When I repaired the piping and put it all back together, I found the habitual wiper noise/juddering disappeared. This appears to be because I made sure the drive mechanism was no longer rubbing against the piping. When I was back in there (the original repair eventually broke down so I replaced the piping) again the juddering returned as I'd inadvertantly allowed the drive to touch the piping. On moving the piping to avoid the drive arm the wipers were fine again. Strange, for all the apparent power in the wiper drive it doesn't take much throw it off.