Small Engines (Lawn Mowers, etc.): front wheel drive problem Craftsman lawn mower, craftsman lawn mower, craftsman model

Question
I've got a Craftsman model 917.378490 front wheel drive mower.  One of the front wheels was sticking occasionally and has now completely frozen up, while the other wheel turns fine.  I removed the wheel and don't see anything unusual with the gear.  I also pulled the gear off and observed a small pin and spring, they don't look worn or failed either, though I'm not sure how they are supposed to fit together.  Any ideas?  Thanks.

Answer
The spring goes into the axle shaft underneath the key then the gear slips over the key.  If you look at the slot you notice in the center it's rounded put the spring in their up and down position.  Next turn the input pulley where the belt goes on to be sure it turns.  Take a look at the gear inside the wheel that's usually the one that fails.  See if the keys still match.  Then go to www.Searspartsdirect.com and on the right hand side of the page you can enter your model number.  This will take you to a parts list and illustrated parts list.  You should be able to I didn't apply the parts you need and order them right there.  I hope this helps good luck on your project.