I just fixed this problem on mine 4 days ago. This IS whats wrong with it..
This will be a 10 dollar fix or less. Take the door panel off, get a 5/16 socket, theres 3 bolts holding the motor on, take the motor off and disconnect wires.
Pop the cover off the motor, will need to tap two different places to get it off, you will see where to hit.
When you get the cover off, you will see the problem, theres a lot of broken pieces of plastic in there. Clean all that out from the gear, NAPA sells the three little plastic bushings for about 3 bucks, but i got the new gear also while i was in there.
If the 3 round bushings dont fit in the holes, just sand them down or what i did, take a razor and shave some off. (its very soft plastic.)
When taking off the metal gear dont loose the collar pin, they break kinda easy and fly across the room. This is a very simple job, a kid can do it.