The John Deere MX6 rotary cutter is one of the most reliable and widely used implements in the John Deere MX series.
In this post, we’ll look at the most common John Deere MX6 problems, what causes them, how to fix them, and practical tips to keep your cutter running smoothly for years.
John Deere MX6 Problems
1. Gearbox Leaking Oil
Problem:
One of the most reported issues with the John Deere MX6 is gearbox oil leaks. This can happen around the output shaft seal, input shaft, or gearbox cover. When the oil level drops, it can lead to overheating or premature gearbox failure.
Causes:
- Worn or damaged oil seals
- Overfilled gearbox
- Loose bolts on the gearbox cover
- Worn bearings are causing seal misalignment
Fix:
- Check the oil level regularly and refill with EP 80W-90 gear oil as recommended.
- Replace any leaking seals immediately.
- Clean the gearbox vent, clogged vents can cause pressure buildup and force oil out.
- If the gearbox feels noisy or has play in the shaft, inspect bearings for wear and replace if necessary.
Tip: Always check for oil leaks before and after mowing sessions, especially if you mow in rough terrain.
2. PTO Shaft Problems
Problem:
Another frequent issue is with the PTO (Power Take-Off) shaft not engaging smoothly or vibrating excessively during operation.
Causes:
- Incorrect PTO shaft length (too short or too long)
- Worn universal joints or yokes
- Lack of lubrication on the PTO shaft
- Bent or damaged shaft from hitting obstacles
Fix:
- Ensure the PTO shaft matches the correct length for your tractor setup; the MX6 requires a minimum overlap of one-third of the shaft length.
- Grease all fittings on the PTO shaft regularly.
- Replace worn cross bearings or damaged sections.
- Balance the shaft if you notice vibrations during operation.
Tip: Avoid making sharp turns with the cutter engaged—it stresses the PTO shaft and can lead to premature wear.
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3. Blades Not Cutting Evenly
Problem:
Uneven cutting height or streaks in the field are common complaints among MX6 owners.
Causes:
- Dull or damaged blades
- Bent blade carrier (stump jumper)
- Incorrect leveling of the cutter deck
- Build-up of debris under the deck
Fix:
- Sharpen blades after every 8–10 hours of mowing.
- Inspect the blade carrier for bends or cracks.
- Adjust the leveling using the tailwheel and top link until the deck is slightly lower at the front (about ½ inch).
- Clean the underside of the deck to remove caked debris.
Tip: Always balance the blades when sharpening. An unbalanced blade can cause vibration and gearbox stress.
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4. Tailwheel Problems
Problem:
The tailwheel assembly often develops wobbling or seizing issues, especially after long use in dusty or muddy conditions.
Causes:
- Worn bearings or bushings
- Bent spindle or fork
- Lack of grease in the pivot area
- Overloaded or misaligned tailwheel
Fix:
- Inspect and replace damaged bearings.
- Check the spindle for straightness.
- Lubricate all zerk fittings frequently.
- Adjust the tailwheel height to match your desired cutting level.
Tip: Keep an eye on the tailwheel pivot bolt; it can loosen over time and cause misalignment.
5. Deck Rust and Paint Peeling
Problem:
Exposure to wet grass and debris can cause rusting or peeling paint on the MX6 deck, especially on older units.
Causes:
- Poor cleaning after mowing
- Chipped paint exposing bare metal
- Long-term storage outdoors
Fix:
- Wash the deck thoroughly after each use and let it dry before storage.
- Scrape off rust and apply a rust-inhibiting primer followed by John Deere green enamel paint.
- Consider applying a wax or rust-preventive coating underneath the deck.
Tip: Store your cutter under cover or in a shed to prevent moisture damage.
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6. Noise and Vibration
Problem:
Unusual noise or vibration from the cutter often indicates imbalance or mechanical wear.
Causes:
- Unbalanced or damaged blades
- Loose gearbox bolts or blade carrier
- Worn output shaft bearing
- Build-up of debris on the blade carrier
Fix:
- Tighten all bolts and fasteners before use.
- Clean off any debris from the deck and carrier.
- Replace bearings or components showing excessive play.
- Ensure blades are balanced and mounted correctly.
Tip: Never ignore abnormal vibration—it can lead to major gearbox or driveline damage.
7. Slip Clutch or Shear Bolt Issues
Problem:
The slip clutch or shear bolt system is designed to protect the driveline, but if not maintained properly, it can fail to engage or slip excessively.
Causes:
- Rusted clutch plates
- Worn friction discs
- Incorrect torque on shear bolts
- Failure to loosen the clutch before storage
Fix:
- At the start of each season, loosen the slip clutch bolts and slip the clutch briefly to remove rust.
- Replace worn friction discs when slipping occurs under light load.
- Use the correct grade and torque for shear bolts as specified in the MX6 manual.
Tip: Keep the slip clutch covered from moisture when the mower is stored.
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8. Skid Shoes Wearing Out Quickly
Problem:
The skid shoes on the sides of the deck wear down quickly when used on rocky or uneven ground.
Causes:
- Frequent contact with rough terrain
- Thin or low-quality replacement skid shoes
- Improper cutting height adjustment
Fix:
- Adjust the cutting height to minimize ground contact.
- Replace skid shoes with thicker, reinforced versions.
- Inspect frequently and rotate if possible to extend life.
Tip: Avoid mowing with the deck too low, as it increases wear and fuel use.
Preventive Maintenance Tips
To reduce the chances of these problems:
- Grease all fittings regularly (especially PTO, tailwheel, and gearbox).
- Check blade sharpness and balance every few uses.
- Clean the deck after every job.
- Store indoors or under cover.
- Follow the John Deere MX6 service schedule for oil changes and inspections.
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Final Thoughts
The John Deere MX6 rotary cutter is a dependable implement when properly maintained. Most of its problems, like gearbox leaks, blade imbalance, and PTO issues, stem from wear or neglect, not design flaws. Regular inspection, lubrication, and cleaning go a long way in keeping your MX6 cutting like new.
Whether you’re clearing brush, maintaining pastures, or trimming roadside vegetation, understanding these common issues helps you extend your equipment’s lifespan and avoid costly downtime.
