My self propelled does not work either - its a Troy Bilt 21" model 12av566n711. Have taken the transmission apart and everything looks O.K. Belt has been replaced and is tight. The shifter fork is not moving over far enough to engage mechanism - needs to move about 3/16" more in order to engage the front wheels. Can push the shifter fork over the 3/16" with a screw driver and it works O.K. but need a permanent solution.
Anyone else have this problem?