Actually the mtd and cub cadet I have both have practically 0 drag and uses full roller bearings for shaft ends. Without the auger pulley brake it'll stay turning for about 20sec and has a gear ratio of about 8.8:1. Already done the homework. Not every machine is the exact same. Old machines are slow an horrible but modern machines can be found cheaper than the old crappy ones that don't even run if you look in the right places. "Collector's Deal"
That's probably the momentum of the big heavy impeller and pulley driving the auger, not the momentum of the spinning auger back-driving the impeller.
With the brake disabled, try turning the auger by hand. It's not just the gear ratio, it's the nature of a worm drive.
It's like trying to remove a bolt from a threaded hole by pulling on it. In an ideal world, (ie, zero friction), applying a longitudinal force to a thread would cause it to start turning, but it just doesn't work out like that.
Some older units did use a ring and pinion gear drive (like the rear end on a car, minus the differential) for the augers. Those would be good candidates for such a use. They will be easily identified by their unique shape. The newer models that can be had cheaply are also made cheaply, with die cast gearbox housings. I just don't see them holding up.
When I built my rat wagon, I had the exact same initial thought of using a snowblower auger box for the final drive, and simply running a shaft up underneath the tub with a one-to-one chain drive off the clutch to turn it. My prior knowledge of gearboxes and drivelines told me it wouldn't work out very well, and upon doing some research online, I discovered that without an overrun clutch on the output side of the box (in this case it would have to be in the wheel hubs), worm drives are a poor choice for vehicles because of the reason I mentioned.
It's also the reason that worm Drive gearboxes are favored in industrial applications, where rollbacks are a concern, such as inclined conveyor belts, bucket elevators, etc. The design does not lend itself to being driven by the output shaft, which is exactly what happens in an unpowered coast, be it forwards or backwards.
