10 John Deere 6400 Problems With Easily Fixing Tips

The John Deere 6400 is another popular tractor among homeowners. This powerful lawnmower delivers 100 horsepower, making all mowing jobs smooth and quick. However, despite its top-notch features and performance, the John Deere 6400 can disappoint you.

Common problems include faulty fuel systems or water pumps, clogged radiator films, damaged hydraulic pumps, engine not starting, broken gear, and more.

If you are considering buying or already owning one, this article will guide you by discussing every common problem you can suffer with the 6400 model and its leading causes. And the best thing is that you will also learn easy fixing tips for each issue.

So continue scrolling down!

Common Problems With John Deere 6400 Lawnmower & Their Fixing

Common Problems With John Deere 6400 Lawnmower & Their Fixing

The John Deere 6400 is a sturdy lawn tractor packed with the best features that make it coveted among tractor enthusiasts. But like other John Deere tractors, this model is also prone to malfunctions.

Below we will explore the typical malfunctions that the John Deere 6400 can manifest, especially after many days of use.

1. Auto-Quad Transmission Failure

Your John Deere 6400 tractor’s Auto-Quad transmission system can wear down and fail. This is more frequently seen in regularly used mowers.

The key reason behind the Auto-Quad transmission failure is that your machine might lift heavier things than recommended.

Suppose your John Deere 6400 mower is suffering from this transmission issue. In that case, it will show symptoms like the machine isn’t moving smoothly or while reversing.

The Fix:

First, turn off the transmission and then reach the Auto-Quad transmission system. Then, you can try to repair the system or call a mechanic to rebuild it.

2. The Engine Is Overheating

Another common problem you can experience with this model is overheating of the engine. If you see a red gauge in your machine, it’s likely due to overheating. Apart from this, overheating will turn on the warning buzzer.

However, overheating can happen due to some water pump commotions. In addition, it can wear down if not properly maintained or if there’s any leakage. Other culprits for overheating can be clogged radiator films and low oil levels.

The Fix:

  • You have first to detect the real cause behind the overheating problem.
  • Check the water pump first to see if it’s damaged. If so, replace it with a new one.

After that, inspect the radiator films for any clogging. After pulling out the radiator screen, clean it. In addition, clean the dirt from the radiator’s backside using water.

Low oil level causes overworking of the engine, which increases the temperature. So you must regularly check the oil levels to prevent such issues. If the oil level is low, add it to the recommended level.

3. Complicated Shuttle Shift

Operating the John Deere 6400 mower with a problematic shuttle shift will be hard and tiresome. Improper shifting of transmission gears causes shuttle shift issues. Eventually, it becomes quite challenging for the operator to change the gears.

A leading cause of shuttle shift commotions is the faulty clutch system. An incorrectly placed connection between the shifter and transmission could result in a problematic shuttle shift.

The Fix:

The first step in fixing this issue is properly set the linkage. If it doesn’t solve the problem, check the clutch to ensure it’s damaged.

However, you must remove the transmission’s front cover and inspect the clutch. If you find it faulty, change it to fix the problem and boost performance.

4. Water Pump Failure

Water pump commotions seem like a common problem with John Deere mowers. Interestingly, water pump issues can occur naturally. There might be no specific reasons behind it.

However, the few factors that can contribute to water pump problems include leakage in the pump system and periodic pump maintenance.

If there is any issue with the water pump, your John Deere mower will overheat. The gauge will turn red, activating the overheating warning buzzer.

The Fix:

The only way to deal with a problematic water pump is to replace the old one with a new one.

5. Steering Issues

You may find it difficult to turn the steering wheels or to keep them in place. Besides the difficulty in mowing, steering issues can cause accidents. Factors like low hydraulic oil, steering cylinder problems, and damaged steering pump usually contribute to such issues.

The Fix:

You will find a locking gas cylinder at the tilting point of the steering. Replacing a faulty one can solve the issues.

Check the surge relief valve to clean it. Replace it if required. Apart from these, disassemble the remote valve for improved performance.

Next, check the hydraulic oil level. If you find it limited, add more oil immediately to fill it up. Or repair the faulty steering pump and cylinder.

6. PTO Issues

New owners have reported that their John Deere 6400 mower suffers from PTO problems. Your tractor with PTO issues will have symptoms like slippage and stripping splines.

While slippage may not be a catastrophic problem, stripping splines will need quick action.

The Fix:

To resolve PTO issues, cut off the electric section and fasten the PTO solenoid with the unique lock solenoid directly. After this, remove the brakes after depressing the lock until it becomes adjustable with the PTO.

Also Read: How to Fix John Deere Fuel Shut-Off Solenoid Problems in 5 Easy Steps

7. Hydraulic Issues

This is another typical problem with this John Deere model. However, hydraulic pump problems need prompt attention because it significantly degrades the mower’s performance and functionality.

Predominant symptoms of hydraulic issues include damaged steering and fluid leakages. If you encounter any of these signs, stop running the tractor immediately.

The Fix:

  • Inspect the hydraulic pump system. If it’s damaged, change it immediately.
  • On the other hand, dirt and debris can accumulate in the hydraulic pump, leading to problems. In that case, check the filter to see if it has dirt or debris buildup.
  • Clean the gauze, and if the pump malfunctions with dirt, you must change the filter.

8. The Engine Isn’t Starting

You will face this engine issue with almost all tractors, including the John Deere 6400 model. Various factors, including plugged fuel injector pumps and empty fuel tanks, can prevent the engine from starting.

Other factors contributing to this issue are dirty radiator fin or fuel, damaged or dead battery, and lack of coolant.

The Fix:

All the causes mentioned above have an easy solution. However, it would help if you found the right reason before resolving the issue.

9. Faulty Brakes

John Deere components, including the brakes, are designed to last several years. However, heavy usage can easily damage the brakes.

The fact is that the disc becomes worn out and gets damaged slowly. Apart from this, dirt particles accumulate inside the suction screen of the rear disc housing.

The Fix:

You can replace the worn discs, but these discs are pretty costly. Thus, it’s better to properly maintain them to prevent them from getting damaged.

If the discs get damaged, you must replace them with new sets. On the other hand, check the rear disc suction screen and clean it if it’s dirty.

10. Gear Break Down

It’s a rare problem with John Deere mowers that can trouble you. Gear can often get weary over time.

If the gear fails, your tractor will produce weird noises from its front axle after starting it.

The Fix:

You will have to open the axles up in case of failed gear to reach the gears. Then, purchase new gears and install them, replacing the old ones.

John Deere 6400: Customer Reviews

John Deere 6400 - Customer Reviews

The John Deere 6400 is powered by a dynamic four-cylinder turbocharged diesel engine and has an impressive 76.4kW power rate. In addition, this robust little tractor packs four types of transmission that let you choose the correct work speed for specific tasks.

Consumers appreciate its highest reverse speed of 29.9km/hr and highest forward speed of 30.1km/hr. The tractor’s fuel flow rate is ideal for large landscapes and farms. Moreover, its cast-iron body ensures it will accompany you for many years.


The John Deere 6400 tractor has many downsides, but they are easy to fix. Considering the good features, this model is undoubtedly a worthy choice. Unfortunately, like any machinery, every tractor is prone to malfunction.

Fascinatingly, the most common problems with the John Deere 6400 can be easily resolved without professional help. This article explains to you all the possible issues and solutions to let you fix them quickly.


How wide is a John Deere 6400?

A John Deere 5400 features a 94.5-inch wheelbase with a cab height of 105.9 inches and a length of 165.7 inches. 

How long can a John Deere 6400 run?

A John Deere 6400 engine generally claims to last nearly 6000 to 8000 hours. However, the engine can run up to 10,000 hours with proper maintenance. 

What is the horsepower of the John Deere 6400?

This John Deere lawn tractor can deliver 100 horsepower, which equals 74.6kW.

About Jennifer Igra

Growing up in Brooklyn, New York City known for it’s green gardens. Jennifer, a 30 year old gardener and green living fanatic started Igra World to share her gardening journey and increase gardening awareness among masses. Follow Igra World to improve your gardening skills.

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