1. Move the freewheel on the shaft. Does she move freely? If not, replace it.
2. Rotate the freewheel in both directions. Does it lock in one direction and rotate freely in the opposite direction? If it doesn't block in either direction, or if it blocks in both directions, replace it.
3. If the starter drive gear is worn or damaged, replace the freewheel assembly; the gear is not supplied separately.
4. If the starter drive gear teeth are damaged, check the condition of the torque converter ring gear.