Small Engines (Lawn Mowers, etc.): lawn mower, lawn mower parts, model craftsman

Question
QUESTION: i have a craftsman 5.5 honda engine model 917-377790 rear drive mower gears on rear wheels will not engage into gears on tire shaft  belt is driving rear wheels roll freely but no power to them how can i fix? thank you  JOE

ANSWER: Are the rear wheel keys installed?
Eric

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QUESTION: can you explain or diagram problem.  i have no experience with power drive mowers

Answer
Parts diagram list link:

http://www.searspartsdirect.com/partsdirect/part-model/Craftsman-Parts/Walk-behi

Part number 52.  Sometimes dirt and grass build up in the wheels and the keys causing them not to work.

Eric