When the window goes up it hits the stop but motor tries to keep pushing it up. Sounds like gears slipping pust each other. When the window goes down it goes about a third of the way and then makes a lot of noise like slipping gears. I am thinking it is not a bad motor since it still runs. Your thoughts on what is broken appreciated.

 

I had the same exact problem as you. My window would only go down about 1/4 of the way and then stop and make a horrible grinding noise. One of the gears is stripped. I just put a new motor in. Im not sure if you could just replace the gear or not since I think its in the motor. Might as well put a new one in if you are going to go through the trouble of taking the old one out.