Small Engine Troubleshooting Problems? Ask a Mechanic Now.
Does reverse work? Have you checked the drive belt?
See the Deere link above.
Hydrostat transmission should work equally in forward and reverse. You just reroute the oil flow to change direction. Have you raised it up in jack stands and ran it to see if there is something obvious knocking?
OK> trying to answer between birthday supper!
!! I understand, I have plumbing problems to take care of!