Both my front window regulators on my '80 model 116, 300SD are shot. I have two acceptable replacements, and began work on the passenger-side this afternoon. I have disconnected all the nuts and bolts that retain the regulator to the window frame, plus all the n's and b's that keep the motor attached to the door panel. even the door stop is now loosened. Problem is that I STILL cannot coax the blasted assembly out of the door frame. The front of the assembly seems or acts as if it is hanging up on something near the front edge of the door. I cannot see what it is hanging on, but wonder if one of the more experienced techs here could give me some guidance. Do I need to loosen the front "rail" that helps hold the window in its "frame"? At any rate, I am at a loss, and would appreciate any suggestions. Trying to get this baby ready to sell.

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1980 300SD 146K miles.