Snow Blowers

I have aHusqvarna 1140SBEXP two stage snow blower. When the engine is running, the impeller turns, however, the auger does not. I've looked at the parts page and I don't see how the gear system works or parts for it in the housing in the center of the auger shaft. Is there a cause for this? The auger turns but stops when encountering snow. The rotation is much slower than what I am used to seeing on this machine. Thanks for any help.