I found something similiar when throwing recyled snow....everyone keeps telling me to slow down but it seems my Toro works better in a higher gear. I thought the gears were only for wheel speed and had nothing to do with impeller speed?? Well thats what I thought anyway but it seems it throws better in a faster gear (most of the time anyway).
You are correct sir; the gearbox only changes wheel speed, and the auger and impeller are driven separately.
The reason speed makes a difference, is that snow is fed more quickly into the auger, which in turn feeds a more steady supply into the impeller. In higher gears, incoming snow, under pressure from the auger, pushes snow ahead of it through the impeller and maintains a steady flow. Faster snow feed is more important when the snow is heavy, wet, more likely to ice up and resistant to flow. Of course,the limiting factor is the engine's ability to process the density/weight of the flow.
I'm starting to think that the Toro's impeller recycling feature is designed to allow faster speeds in heavy snow. My first impulse was to slow down also, because I used to have an MTD without the impeller recycling.
This is only my observation, based on this experience, so I'm not claiming expertise.
