might be a broken E clip inside it, where it holds the Mouse Trap Fork in position on the Rube Goldberg Shaft. with cad removed and vacuum attached to it from a hand pump or the engine, you should be able to see it operate and move the shift fork back and forth.

if the repair is not simple, be careful about the price of a replacement. you can get a dorman or cardone for not too much money, or better get a posilok cable and be done with it. don't pay dealer price for a replacement.