sorry another 67 coronet wagon question

i was wondering if you could help me.i just bought a 67 wagon .the tailgate was down when we went to look at it so i know the rear window will go down.now that we have it home i cant get the rear window down.the crank moves slightly then there is a hard stop in either direction.the window moves maybe an 1/8 of an inch and stops dead.the po said he never locked it and it worked fine for him.i have a key and it turns it about 90 deg but does the same in either position.it seems to be locked somehow .could there be something simple im missing?i think the next step is to remove the whole lock assembly but it looks like its bolted from the inside and hidden behind the gears.any ideas? does anyone know where i might get an exploded view of the tailgate components?