Hi Greame,Thanks for all the input. Your description is very accurate. The plastic worm drive on the big sprocket wheel is off about half a teeth now. There is not enough play to allow the motor to move freely yet. I have yet spent enough time to look at the whole thing to see where I should start lubricating. There is some grease left, but it seems a little hard. I will clean it out, then attempt to re-mesh the teeth along with lubricating the track (which I don't know where), and see the window will bulge. Will the sprocket wheel slide out of the cog, if you remove the motor assy? Drop me a line if you happento know.ThanksThai