The John Deere Z425 zero turn lawn mower operates on two separate drive systems for each drive wheel. This hydrostatic system allows the mower to turn each wheel independently from the other. Because of this, it can be extremely difficult to push if the mower fails to start. Not to worry, there are hydraulic release valves that allow the Z425 to free wheel making easy to push.
Turn off the engine and and remove the key form the ignition switch.
Set the parking brake and raise the operator's seat. Locate the release valves on the inside of each of the drive pumps. Turn both of the release valves half a turn counterclockwise. Unlock the parking brake.
Push the lawn mower to the desired destination. Because of hydraulic drag, the machine push slowly. Turn the release valves clockwise until they are hand tight.
Set the parking brake.