Small Engines (Lawn Mowers, etc.): Self propelled Craftsman mower, craftsman model, rear wheels

Question
I have a 5.5 year old 6.5 HP self propelled Craftsman walk behind mower.  This model has the large rear wheels and regular front wheels.  Sunday, while my husband was mowing, the self propelled feature just died.  We looked at all of the linkage cables and they appear to be fine.  Any suggestions?

Answer
I have to have the Craftsman model number to know the type of mower style to help. Otherwise, you can remove the plastic cover on the top of the mower, and check the drive belt. There are a lot of parts involved for some of the drive systems, and some are more frequently serviced. Without the Craftsman model I don't know the setup of that mower.......Tom