My girlfriend has a vintage Schwinn with a Shimano 3CC 3-speed hub and coaster brakes. After a bit of biking in the rain she mentioned that the shifting was wonky. I tried to be a hero and adjust them by adjusting the cable housing stop band, but that seems to have made the problem worse. Now the shift won't hold at all. One possible contributing factor: When I was adjusting the cable housing stop band, the lack of tension in the cable seemed to free the cable in the shifter. My girlfriend opened it up and all the parts exploded out. It's possible that when I put it back together I messed it up.

From examining the setup it seems I'm missing something: What makes the shift hold at all on these bikes? I've followed the instructions here, but as far as I can tell, the push rod just wants to be out as far as it can go (i.e., 3rd gear). Am I missing something? I can post more pics/info as needed.