Acme nut whiffle tree's
The whiffle tree is the threaded rod mounted on the bottom of the pop up. A drawbar runs up and down the bar, and pulls or release the cables.
Plastic delrin nut / acme screw whiffle tree. Your original Coleman or Fleetwood whiffle tree may a white plastic nut at the center of the drawbar.
There were two types of whiffle trees used. Ball bearing and plastic delrin nut. This style of plastic nut tree is more commonly found on smaller box sized units.