Outdoor Power Equipment and Small Engines - transaxle quit

I have a craftsman lawn tractor model 917.273220 with a transaxle model 222-3010L . Today while mowing I stopped for a moment to miss a hole in the yard and when I resumed I had no forward gear. I could go in reverse about 20 feet and then I lost reverse also. I put the tractor in free wheel position to get it to the barn and it made a ratcheting sound all the way.When I got it in the barn I put the engagement control back in the engaged position. With it engaged the tractor can be pushed which should not happen. Also it makes the same ratcheting sound that it made in the freewheeling position. Any help would be appreciated.
Thanks Fordman

The first thing I would check is the keys on both rear wheels and axle. If either one was to shear off then the unit would quit moving. It's also possible the problem may lie in the differential portion of the axle or hydro unit.