I have a snapper model I524 snowblower that the auger blades aren't turning properly. ne,?

theshear pins are fine,the impeller turns fine, but the auger blades turn erratically and slower than usual. Is there a seperate belt for the auger or is it driven bt the same one as the impeller or could it be the worm gear in the auger housing wearing out? thanx in advance for any help.