Any idea about why the auger on my 1970's Ariens 724 snowblo...

Any idea about why the auger on my 1970's Ariens 724 snowblower won't ngage ?. Shear pins are not the problem. When I attempt to engage the auger using the lever, the engine sound changes slightly but the blades will not turn ? Might it be a broken belt ?? Thanks for any help someone might offer.

Check to see if the drive nelt and pulley are turning under the plastic cover between the auger assembly and the engine.If the pulley is turning, replace the belt . I have found that a key is on the drive shaft and may have fallen out , it mechanically joins the pulley to the shaft. You will need to split the two assemblies to replace the key , this is very simple . Good luck