Worm gear from a Ford Model TT (Ton Truck).
The owner’s manual does not say why the truck uses a worm gear final drive. I have to assume given the Model T’s wimpy transmission band brake, the worm drive would prevent a run away if the brakes failed or the truck stalled going up a steep hill.
The final drive reduction was 7.25:1 making for a top speed of just about 25mph, vs. the Model T’s 40 or so.
