John Deere 42 Inch Mower Deck Parts Diagram+ Troubleshooting Guide Vibration can also take place due to nuts or bolts getting loose in blades, pulleys, and mandrels. Also, pulley or mandrel damage can cause it.Sometimes its due to pulley catching dirt or even a blade belt failure. But it can be due to the blade not being balanced.
There are many sources of this wobbling deck problem.
John Deere L120 48″ deck spindle replacement
