Small Engines (Lawn Mowers, etc.): Transmission, shift forks, pulley

Question
   I am helping a friend fix a late 80s craftsman mower. The engine is o.k.. The problem is the transmission. We took it all apart, and took the rear end off. Spinning the top pulley also spins the brake and the gears are right. But it is not turning the wheel.I figure it is in the linkage from the gear to the wheel. Am I right? Or is there something I am missing?
                                  -Thank You

Answer
Spinning the pulley should turn the primary gearset.  The connection from the primary (drive) gearset to the secondary (driven) gearset is made through the shift forks.  They need to engage the appropriate gear (depending on gear you select) in order to transfer power through the transmission.  If the secondary gearset is being engaged and the wheels still don't turn, the issue would be with the differential (final drive).  Hope this helps.