Rabbit

Ok i have an annoying problem with my Wipers. When you turn them on they wipe fine (seems a little slow) weather its intermittent or high or low. When you turn them off OR they stop for the intermettent delay they will just kinda shake at the resting position, shake quite a bit actually. You can hear it real well, thump, thump, thump and you can see them plain as day shaking there they will not stop EVER. It does stop with the truck off but as soon as you start the truck again (with the wipers OFF) they will continue shaking until at some random time it will stop untill you need to use the wipers again. Anyone have any ideas whats up? It seems to me they park themselves about 1 to 2" higher on the windshield then when i first got the truck. What do you guys think? I cant find any info how to teach the motor where to "Park" like when i replaced motors in other foreign cars.