The engine on my Ariens 926LE snowblower starts and runs just fine. When
I start it, the wheels engage properly but the impeller & augur
initially don't engage. After a couple of minutes they seem to start
working fine. Though occassionally even after running they will fail
intermittently to engage.

The shear pins are fine. The cable running to the augur/impeller control
is fine. I don't think it's an icing issue since I keep the snowblower
inside the garage where it is mostly above freezing and I clean it out
after each use. When the impeller and augur do finally engage they seem
to have good, normal power both in the auger and the impeller.

Any ideas what could be wrong?