Small Engines (Lawn Mowers, etc.): Sears lawn tractor 6years old, craftsman no motion

Question
I have a Craftsman 917.272281 with a 323-0510 hydro gear, sometimes goes under the model # 173839.  I can not get it to go forward or reverse, also will not go into neutral to be able to push.  When i try to go forward or reverse it sounds like a belt is slipping or being chewed up.  Replaced belt but problem still there.  Belt is moving the way it is supposed to, no problems there.  Is it the hydro gear?  I opened it up and oil was full, gears look fine.  Any help.

Answer
It could be the directional check valves which are internal but it's probably the bypass valve.  Follow the linkage for the freewheel engagement to the lever on the transaxle that engages the bypass.  See that it's moving through its range.  It can also stick or leak.  Fixing this might require disassembly.

You can try purging the system.  Jack the rear wheels off the ground and with the the bypass valve in freewheel, and the engine running, slowly move the shifter from forward to reverse five or six times.  then do the same thing with the bypass in the motion position.  You need to check the level of oil when you do this as if there is air in the system, the oil level will drop.  The transaxle uses 20W50 engine oil.  Let me know if you have any questions.  Thanks, PK.