John Deere 850 Problems: Common Issues and Fixes

If you’ve ever faced the frustration of dealing with a seemingly endless list of issues while trying to maintain your John Deere 850, you’re not alone. From mysterious vibrations to engine hiccups, it can feel like a never-ending battle to keep your mower in top shape. But fear not, there are practical fixes and preventive measures that can help you conquer these challenges and get your John Deere 850 back on track. Stay tuned to uncover the solutions that will ease your maintenance woes and keep your mower running smoothly.

Key Takeaways

  • Blade imbalance and vibrations are common issues.
  • Regular maintenance prevents damage to mower deck.
  • Engine component issues may affect cutting performance.
  • Check and balance blades for optimal performance.
  • Follow maintenance schedule to avoid problems.

Mower Deck Problems

John Deere 850 tractor with a leaking hydraulic hose, a clogged air filter, and a smoking engine.

When encountering issues with the mower deck on your John Deere 850, inspect the blades and belt for wear and proper alignment. Begin by checking the blades for any signs of damage or dullness. Dull blades can lead to uneven cuts and put extra strain on the engine. Replace any blades that are worn out or damaged to guarantee a clean and efficient cut.

Next, examine the mower deck belt for any signs of wear, cracking, or stretching. A worn-out belt can cause the blades to rotate inconsistently or not at all. Confirm the belt is properly tensioned and aligned to prevent slipping or damage during operation. If the belt shows signs of wear, replace it promptly to avoid further complications.

Regular maintenance of the mower deck, including blade and belt inspection, is essential to ensure top performance and longevity of your John Deere 850. By staying vigilant and addressing any issues promptly, you can keep your mower deck in top working condition, allowing you to tackle your lawn care tasks with ease and efficiency.

Engine Issues

Inspect the engine of your John Deere 850 for any signs of irregular performance or abnormal sounds to identify potential issues early on. Common engine problems in the John Deere 850 include issues with the fuel system, such as clogged filters or a faulty fuel pump. If you notice decreased power output, difficulty starting, or sputtering during operation, these could indicate fuel system issues.

Another common problem is overheating, which may be caused by a malfunctioning thermostat, low coolant levels, or a faulty water pump. Keep an eye on the temperature gauge and address any overheating promptly to prevent serious damage to the engine.

Regular maintenance, such as changing the oil, replacing air filters, and inspecting spark plugs, can help prevent many engine issues. If you encounter any problems, addressing them promptly is crucial to avoid more extensive damage and costly repairs.

Transmission Troubles

John Deere 850 mower deck with visible common issues such as belt misalignment, blade damage, and clogged discharge chute, alongside tools and parts for fixes.

To diagnose potential transmission issues in your John Deere 850, carefully monitor for any unusual noises or erratic gear shifting behavior. If you notice grinding sounds while shifting gears or delays in gear engagement, it could indicate problems with the transmission system.

Another common symptom of transmission troubles is the tractor slipping out of gear unexpectedly. When troubleshooting these issues, start by checking the transmission fluid level and condition. Low fluid levels or dirty fluid can lead to poor transmission performance.

Inspect the transmission linkage for any signs of damage or misalignment that could be affecting gear shifting. Additionally, worn-out clutch components can also cause transmission problems in your John Deere 850.

Regularly servicing and maintaining the transmission system can help prevent these issues. If the problem persists, it’s advisable to consult a professional mechanic for a thorough diagnosis and repair to ensure the best performance of your tractor.

Belt Tension Adjustment

Adjusting the belt tension on your John Deere 850 is crucial for maintaining peak performance and preventing premature wear on the drive system. Incorrect belt tension can lead to slippage, reduced power transmission, and increased strain on various components. To guarantee your equipment operates smoothly, follow these steps to adjust the belt tension properly:

Steps to Adjust Belt Tension
1. Locate the Tension Adjustment Bolt:
2. Loosen the Bolt:
3. Adjust the Tension:

Carburetor Maintenance

John Deere 850 tractor with a visible engine compartment. Highlights common engine issues like overheating, leaks, and belt problems, alongside tools for fixing.

Regular cleaning and maintenance of the carburetor on your John Deere 850 is essential to maximize engine performance and fuel efficiency. The carburetor is responsible for mixing air and fuel in the correct ratio for combustion within the engine.

Over time, dirt, debris, and varnish can build up in the carburetor, leading to issues such as poor engine performance, hard starting, and reduced fuel efficiency.

To maintain your John Deere 850’s carburetor, start by regularly inspecting it for any signs of buildup or damage. Use a carburetor cleaner to remove any dirt or varnish that may be affecting its performance. Pay close attention to the small passages and jets within the carburetor to ensure they’re clear and free of obstruction.

Additionally, consider installing a fuel filter to prevent contaminants from reaching the carburetor.

Transmission Fluid Check

Monitor your John Deere 850’s transmission fluid level regularly to guarantee proper operation. Signs of contamination, such as a burnt smell or unusual color, indicate potential issues that need to be addressed promptly.

Regular maintenance of the transmission fluid can help prevent costly repairs down the line.

Fluid Level Inspection

Verify transmission fluid levels are within the recommended range by conducting a thorough inspection using the following steps.

To check the transmission fluid on your John Deere 850, start by parking the tractor on a level surface and engaging the parking brake. Locate the transmission dipstick, usually situated near the driver’s seat.

Remove the dipstick, wipe it clean, and reinsert it fully. Withdraw the dipstick again and observe the fluid level. The fluid should fall within the designated range marked on the dipstick.

If the level is low, add the appropriate type of transmission fluid recommended in the user manual. Avoid overfilling, as this can lead to excessive pressure within the transmission system.

Regularly inspecting the transmission fluid level is essential for the proper functioning and longevity of your John Deere 850. By maintaining the correct fluid level, you can prevent potential transmission issues and ensure optimal performance of your tractor.

Signs of Contamination

Examining the transmission fluid for signs of contamination is essential for identifying potential issues with your John Deere 850. Contaminated fluid can indicate problems such as internal component wear, leaks, or overheating. To accurately assess the condition of the transmission fluid, follow these steps:

  1. Color: Normal transmission fluid is typically red or green, depending on the type used. Any discoloration towards brown or black may indicate contamination.
  2. Consistency: Clean transmission fluid should have a smooth consistency. If you notice grittiness or particles in the fluid, it could be a sign of contamination.
  3. Odor: Transmission fluid should not have a burnt smell. A strong burnt odor could suggest overheating or internal damage.
Signs of Contamination 
ColorBrown or BlackNormal: Red/Green
ConsistencyGritty/ParticlesNormal: Smooth
OdorBurnt SmellNormal: Odorless

Regularly checking and maintaining the transmission fluid quality can help prevent major issues and keep your John Deere 850 running smoothly.

John Deere 850 tractor with a close-up of the transmission area showing a leaking seal, worn gears, and a mechanic hand holding a repair tool, surrounded by spare parts.

Blade Sharpening Tips

Maintain the correct angle while sharpening the blades on your John Deere 850 to guarantee the best cutting performance. To ensure ideal results, use a grinding wheel or file to sharpen the blades. Start by securing the blade in a vice to keep it steady during the sharpening process. Maintain a consistent angle of around 30 degrees while sharpening to achieve a sharp edge without compromising the blade’s integrity.

Remember to sharpen both edges of the blade evenly to prevent imbalances that could affect cutting precision. Inspect the blade for any signs of damage or wear before sharpening, as severely damaged blades may need replacement rather than sharpening.

After sharpening, balance the blade to ensure smooth operation and prevent vibrations that could damage the mower deck or engine components.

Regular blade maintenance is essential for the overall performance of your John Deere 850. By following these sharpening tips diligently, you can prolong the life of your mower blades and maintain a pristine cutting experience.

Frequently Asked Questions

How Do I Troubleshoot Electrical Problems on a John Deere 850?

To troubleshoot electrical problems on a John Deere 850, start by checking the battery for proper connections and charge.

Inspect the wiring harness for any signs of wear or damage.

Use a multimeter to test the voltage output of the alternator.

Check all fuses and relays for functionality.

If issues persist, consult the technical manual for detailed wiring diagrams and diagnostic procedures.

What Are the Common Causes of Steering Issues in a John Deere 850?

When steering awry, the John Deere 850 may vex you with worn tie rods or misaligned wheels. These snags can throw your trusty tractor off course.

Check tie rods for looseness or damage, align wheels meticulously, and guarantee steering components are well-lubricated.

Can I Install a Mulching Kit on My John Deere 850 Mower Deck?

Yes, you can install a mulching kit on your John Deere 850 mower deck. Verify compatibility with your specific model and follow manufacturer instructions precisely for proper installation.

Mulching kits typically include blades, baffles, and hardware necessary for converting your mower into a mulching machine. This upgrade can improve grass cutting efficiency and promote a healthier lawn by recycling clippings back into the soil.

What Are the Signs of a Failing Ignition System on a John Deere 850?

When your John Deere 850 shows signs of a failing ignition system, you might notice issues like difficulty starting, engine misfiring, or sudden stalling. These symptoms can indicate problems with components like the spark plugs, ignition coil, or distributor.

Ignoring these signs could lead to poor engine performance or even complete failure. Stay vigilant and address these issues promptly to keep your mower running smoothly.

Is It Possible to Upgrade the Tires for Better Traction on a John Deere 850?

Yes, you can upgrade the tires on your John Deere 850 for better traction. Consider swapping out your current tires for ones with deeper treads and a more aggressive tread pattern.

This modification can greatly improve your tractor’s grip on various terrains, enhancing its performance and efficiency.

Make sure to select tires that are compatible with your John Deere 850’s specifications to maximize the benefits of this upgrade.


In summary, addressing common issues with your John Deere 850 mower is essential for top performance.

Just like a well-oiled machine, regular maintenance and inspections will keep your mower running smoothly and efficiently.

By following these fixes and maintenance tips, you can guarantee that your John Deere 850 operates like a well-tuned engine, cutting through grass with ease.

Keep your mower in top shape to enjoy a pristine lawn all season long.


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