Is it possible to replace only the gear portion of the window regulator?

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Driver's side window suddenly stopped working, followed by a clicking sound, as though the window motor was still running. It finally stopped, and luckily after a few tries, I was able to get the window completely closed. After removing the door panel to further investigate, all cables are tracking correctly, but it appears the gear portion of the motor assembly is shot. Is it possible to replace only that piece or does the entire frame mechanism need to be replaced?