Fortunatly or unfortunatly, I haven't had to mess with the window motors yet. They have always worked great, other than getting stuck in closed psition (usually a forced turm by a screw driver on the gear, releases them). But I am sure others who have done this will have advise. I just saw a note from Ron Dwyer that said the E28 motors will work even though they very tiny, but be prepared to change switches as well, if you car is 72 earlier!!