My craftsman has the same setup and had the same symptoms. Turned out that
the shaft (axle) that the gearbox drives had snapped in half. They must be
fairly weak because I was just mowing the lawn when it broke - mower never
abused. New axle shaft was about $30. PITA to replace, but it's been
working great ever since.

"tomkanpa" wrote in message
ups.com...
It has a gearbox that is powered by a belt from the engine. It doesn't
appear that the belt is slipping. And the arm that engages the gears
moves. Yet there's no power to the wheels. Well, I take that back. On
a level driveway, it will pull itself along at a slow pace. At the
gear box which is part of the axle "jumps up and down." And with the
engine off and the gearbox engaged, the front wheels are locked as if
everything is engaged.
Any ideas on what the problem is?