I did a search on replacing a rear window sliding jaw (why is it called a jaw?) on a W126. I couldn't find anything more specific than 'remove the regulator.'
Okay, I'm to that point. It appears that I have to release the wiring connector from the motor. I can't get it to budge. Does is slide up along the motor axis or radially away from the motor?
On the subject, the glass slides smoothly up and down the track; no binding, no tilting. But there is a bit of drag. It feels as though I can drive over railroad ties without fear of the window sliding down even with the regulator out. Is this as tight as it should be? Is this why the old jaw broke? What clown thought plastic is the way to go?