Auger belt on snow blower keeps coming off

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Either two things come to mind, first I would check the shear pins. When a shear pin is broken, the auger turns but stops as soon as it hits a load (snow). The shaft is turning, but there's no mechanical connection between the shaft and the auger.

The second thing is the belt either needs adjusting or replaced. Belt adjustments should be checked before every winter and are simple to preform. When checking the drive and auger belts, look for glazed running surfaces, and cracking. Either sign means the belt(s) need replacing. Also if the belt(s) have streched beyond their normal adjustment.

Replace auger belt

How to Replace Craftsman MTD 524 Snow blower auger belt

Snow Blower Belts

Since your snowblower is a two stage all metal unit the only thing keeping the snow from shooting out is either a worn out drive belt or a weak engine. The belt is the easy thing to change. Buy a new drive belt too since it is a good time to change both at the same time. The unit actually breaks into two parts at the back of the auger housing to expose the belts for changing. A local shop can do this service for 100-$200 bucks along with an oil change and chassis lube. Not too bad since this will keep your unit running reliably for years to come.

check the belts and belt tension

If I was you I would check key way to see if it has sheered off. It is in center of big drive pulley where belt goes on, Just remove nut and slide pulley off to check condition. Best to split snowblower in half. Your snowblower has two main pieces it will be 4 or 6 bolts to separate your machine.

The most common cause of this is the drive belt is worn.
If you remove the cover (usually plastic) in the middle of the snow thrower and look at the belts.
Your operator's manual will show you how to remove the cover and check/change the belts.
The belt closest to the blower assembly drives the auger/blower and the belt closest to the engine drives the transmission.
With the engine not running, have someone depress the drive lever and check the blower belt.
You should only be able to depress the long side 1/2 inch or less. More than that the belt has stretched and needs to be replaced.
On some older blowers you can adjust the tension pulley, but most made in the last 15 years, you can't.
The belt may be frayed on the edges or glazed causing it to slip (it is shiny on the sides of the belt) It may be torn and broke completely.
You can get parts for you Craftsman and most Husqvarana, MTD made models through searspartsdirect.com. You can also get parts through jackssmallengines.com or your local dealer.
If you are unfamiliar with repairing machines take it to your local dealer. They will have a technician troubleshoot and repair the unit.
Feel free to ask any other questions to troubleshoot this problem farther. I know Snow Blowers. Please remember to rate this answer!

does the impeller spin and not the augers.if so check sheer bolts.if neither impeller or auger spins check auger belt.

the problem could be the snow is to heavy for the motor to keep up, if thats the case you may need to upgrade to a more powerful model or try not to overload it. take it a little slower so the motor can keep up. but try tightening the belt. with your pointer finger push down on the belt it should have about a half inch give, if it moves more than that its too loose and probably slipping under load