How to Troubleshoot a John Deere Mower Deck

A tall stand of grass creates problems with a riding mower.

Riding mower decks continue to improve. A 42-inch mower deck was once considered an extra-wide deck. Today, 42- to 52-inch cutting decks are standard. Double- and triple-bladed mowers within this now-standard range of mowers makes short order of a large lawn. With the additional cutting swath comes additional dynamics and moving parts. All moving parts come with the same guarantee. They will eventually wear out and fail. If that were not enough, a number of other issues will eventually bring the wide-body cutting machine to a stop. Troubleshooting a John Deere mower deck can isolate, and diagnose, an existing problem.

Step 1

Inspect the mower deck for bent or damaged components when excessive vibration is a problem. Take a close look at the mower blades--with the engine shut down of course-- to ensure none of them are bent or loose. Mower blades are extremely difficult to repair once they are bent or damaged. If even a single blade is in disrepair, replace the entire set.

Step 2

Sharpen the mower blades if grass appears brown and injured on the tips after mowing. Such a symptom is a result of dull blades. Not only will dull blades damage the lawn temporarily, the torn grass blades become more susceptible to shock and disease. Keep blades sharp at all times to avoid such a condition.

Step 3

Inspect the deck for level if it cuts unevenly. The wider a John Deere mower deck is, the easier it is for it to become un-level and wreak havoc on the lawn. Park the mower on level ground and measure each outside edge of the deck to the ground, and determine the difference. When one side of the deck is 1/4-inch or higher than the other, re-level the deck by adjusting the lowest end of the deck upward. Adjustments for John Deere mower decks are on each side of the mower, next to the lift yokes.

Step 4

Raise the mower deck and slow down the tractor speed when patches of grass are left uncut. For the best mowing results, no more than 1-inch of grass should be cut off at a time. Reducing the mower speed allows the blades more time to effectively cut.

Step 5

Examine the mower deck drive belt if a squealing sound is present while the mower deck is operating. A worn belt stretches and begins to slip on the deck pulleys, creating the irritating tell-tale sign. Other indications of a worn belt are cracks and flat spots along its inside edge. Replace worn or defective mower deck drive belts with a new, original John Deere belt for optimum performance.


Cut grass when it is dry to prevent bogging down the mower.

Slower driving speeds produce a more uniform lawn cut.


Never service or adjust a mower deck while the engine is running.