This is probably what the guts of your snowblower gearbox look like, too. I upended my trusty winter friend today for a look-see when the auger engage lever wasn’t returning. Suspected a broken spring was the culprit and confirmed that, bottom right of this photo. The drivetrain clutch is a model of simplicity: the belt-driven pulley has a rubber platen centre, like a turntable. When you pull on the lever to engage the drive train, you’re yanking that cable on the right, pulling the spinning turntable against the perpendicular rubber wheel attached to the shaft that drives the larger axle gear attached to the wheels. Shifting gears is accomplished by shoving that rubber wheel between the centre and outside edge of the turntable: faster spin on the outside means faster wheel speed. And for reverse, the rubber wheel is shoved to the other side of the turntable, thus turning the driveshaft in the opposite direction.
High-five to YardMaster for shipping my snowblower with a manual that includes a detailed exploded parts diagram. Makes it much easier to get a new extension spring, part number #732-0611. Wish all vendors would support repair/reuse like this, employing standard fasteners so we can crack open and fix what we own.
Hope y’all got your DIY freak on this weekend.