How To Fix John Deere Hydrostatic Transmission System Problems  - Outdoor Power Equipments Troubleshooting & Buying Guide (2024)

Key Takeaway

  • Most of the times, the John Deere hydrostatic transmission problems occur due to less fuel in the oil reservoir, broken hoses or air trapped into the hoses, a worn-out hydraulic pump and sometimes, due to battery problems and engine issues.
  • Start by purging the hydro-transmission system if the tractor hasn’t been in use for a long time.
  • Then, check the level of fuel in the oil reservoir. Maintain sufficient fuel and change the engine oil if it’s too viscous.
  • Check the brake pedal and the clutch. Change them if the pedal linkages or the clutch Cable is broken. If the metallic hose is broken, or too brittle if it’s of rubber, replace it.
  • Change the worn-out hydraulic pump to prevent leakage of fuel.
  • Check if the battery circuits are fused or terminals are corroded. Change the electrical wires if they are broken and connect to the right terminals.
  • Lastly, check the engine and clean the filters if they have any carbon build-up.

Do you love gardening? If yes, I’m sure you must be familiar with the super comfortable John Deere lawn tractors which are very comfortable, have powerful engines ranging from 17.5 hp- 22 hp and a huge 42” deck which makes it a great choice for both flat and hilly terrains. The bumper-to-bumper warranty is worth mentioning when all these stunning features come at an affordable price.

The John Deere lawn tractors have the powershift hydrostatic transmission, the Funk HMD transmission which is a lot technologically-advanced and makes it easy to use the lawn tractor but at times, you might have to deal with some John Deere Hydrostatic transmission problems which can make to difficult to move the tractor.

When a lawn mower or a tractor is equipped with hydrostatic transmission, it has a hydraulic pump to run the engine using the hydraulic fuel which moves through rubber or metallic hoses.

If you’re facing the John Deere transmission problems, it can be due to a hydraulic pump that might be worn-out, or the hoses are clogged, air is trapped into the fuel lines, the fuel starts to leak due to a decayed pump and many such problems.

Today, I have brought an extensive review of the John Deere zero turn hydrostatic transmission problems which will apprise you with the causes and the best solutions of all such problems. So, stay tuned and keep reading!

What causes John Deere Lawn Tractor Transmission Problems?

When we proceed for John Deere hydrostatic transmission repair, the transmission problems might appear complex and strange but surprisingly, it’s very commonly received on most of the prominent lawn tractors and mowers which use the hydrostatic transmission such as the Cub Cadet LT1042, LT1050 , XT1, XT1 LT50, the Ferris IS700Z and the IS2100Z and the list goes on..

Hence, all you need is a thorough diagnosis of the causes and thereafter, you can use the solutions given ahead to tackle all the common transmission problems with John Deere.

Take a look at the possible reasons that can cause the transmission problems on a John Deere lawn tractor.

  1. Inadequate oil in the oil-reservoir;
  2. Defective mechanical parts such as hoses, brake pedal;
  3. The engine oil has become very viscous;
  4. Front Axle fluid has less hydraulic fluid;
  5. The battery terminals are corroded or circuits are fused;
  6. Hydraulic pump and the motor are worn-out;
  7. Fuel is leaking due to a worn-out pump.

Now, let’s find out how these problems can be resolved either by repair or replacing the defective parts.

Troubleshooting The Common John Deere Transmission Problems

The hydrostatic transmission system of a lawn machine is very different from the other mechanisms and thus, the parts a machine has which uses this transmission system, are very distinct. Each part has its own function and lifespan.

Thus, it is very important for you to be well-aware of all the parts before you proceed for the repair.

1. Purging the Hydraulic System;

Most of the time, it is due to ‘cavitation’ that the transmission problems arise on the lawn tractors or the zero turn mower.

Never heard of it? Let me explain-

When you turn on the hydrostatic transmission system of your lawn tractor, there might be trapped air bubbles in the system which is known as ‘Cavitation.’

  • When the hydro-transmission system is dealing with cavitation, it means it has more air than oil.
  • This less amount of oil cannot build sufficient pressure in the system which is required to generate power.

Most likely, cavitation would have occurred if your lawn tractor has not been used for a long time and that is why, the hydrostatic transmission is failing.

Let’s learn how to purge the John Deere to fix a case of cavitation.

12 Steps For Purging The John Deere Lawn Tractor Correctly

  • Step 1 : Start by parking your John Deere lawn tractor on a flat ground. Engaging the brakes, set the rear wheels on the jack stand.
  • Step 2: Now check the oil reservoir. If the fuel is less, add in more fuel as per the manual.
  • Step 3: Now, pull the lever out for disengaging the transmission. To locate the lever, reach out to the backside and remove the box.
  • Step 4: Now, be seated on the tractor for starting the engine and take the throttle control towards the slow position.
  • Step 5: Keep the lever of motion control in the neutral position to disconnect the brake pedal or the Clutch.
  • Step 6: Now, taking the levers of motion control forward, stay put in that forward position for a while. Just after this, reverse the action by pulling the levers all the way back.
  • Step 7: Now, perform this exercise of lever-first-forward-then-backwards at least three times continuously and all the trapped air from the transmission system will be purged out.
  • Step 8: After this, bring the levers in a neutral position and switch the engine off, engaging the parking brakes.
  • Step 9: Check the level of fuel in the reservoir again and add in fuel if required. Now, engage the transmission and bring the tractor down from the jack stands.
  • Step 10: Start the tractor’s engine once again and disconnect the brakes.
  • Step 11: Take the levers forward and run the tractor for some 6 feet. Now, run the tractor in reverse for about the same length.
  • Step 12: Now, change the lever position from forward to neutral and run the tractor again in both the forward and the backward direction one after another, at least thrice.

With these steps, you can purge your lawn machine that has not been running due to failure of the hydrostatic transmission system and purging it correctly will help you operate your lawn tractor or mower, in the right way.

2. Check the Hydraulic Fuel System;

If the transmission problems have not been solved after purging the John Deere tractor, let’s inspect the fuel system and check if the fuel is contaminated or filters are clogged.

  • First of all, check all the parts of the engine for any damage. Inspect the filters, the carburetor for any damage. Change the parts that are totally worn-out.
  • The main culprit in the hydraulic fuel system can be a worn-out hydraulic pump. If the pump has its plastic lining coming out or the insides of it are rusted, it won’t hold the fuel correctly, won’t build pressure in the combustion chamber and thus, won’t generate power for the tractors’ engine. Thus, change the pump if required.
  • Check if the engine has all the essential settings in the correct place. If not, adjust them as specified in the manual.
  • Thereafter, check the thickness of engine oil. Change the engine oil if it has become too viscous. Viscosity of the oil increases when the air filters are clogged and disturb the fuel-air mix in the tank. Too viscous an oil can lead to a smoking engine which is potentially dangerous for the lawn tractor.
  • Inspect all the wires and the hoses closely. If the hoses or clamps are broken, change them with new ones.
  • Lastly, check the tractor’s oil reservoir. Change the fuel if it’s not been changed for a long time and has dirty residual particles floating in it.

3. Fix the Engine Issues;

If the John Deere tractor’s engine has been bearing any issue, it would not let the hydrostatic transmission system work to build power.

  • Check the brake pedal. If it’s non-functional, it is the foot pedal or the linkages that are broken. In that case, change it if it’s broken.
  • Next is to check the clutch. If the clutch is not working, check the clutch cable. Replace the clutch cable if it’s broken.
  • Check the spark plug and the safety switches. and ensure it’s clean and working.
  • Change the fuel if it’s old and add in more fuel if it’s less.
  • If the engine has started consuming oil excessively, inspect the engine’s choke and ensure it’s open fully.
  • Check the fuel filters, the air filters and the carburetor. Clean them if they’re clogged but change the filters if they’re decayed otherwise they can leak fuel.

4. Hydraulic and Steering Fluid Change;

If none of the above mentioned solutions have worked, check the condition of the hydraulic fluid. John Deere uses Hy-Gard low viscosity hydraulic fuels which are exclusively manufactured by John Deere engineers for the John Deere lawn machines.

To check the hydraulic fuel, take off the oil-reservior’s cap that is given behind the driver’s seat on the John Deere lawn tractor.

  • If the hydraulic fluid is old and contaminated, it will affect the functions of the front axle and the steering system. Old hydraulic fuel causes a number of steering problems on the lawn mowers and tractors.
  • Thus, as recommended by John Deere, change the hydraulic fuel after using the tractor for about 50 hours for the first time. Thereafter, you can wait to use the tractor for 100 hours to change the fluid.

5. Check the Electrical Connections;

Solving electrical problems are generally not everyone’s cup of tea but you can resolve the electrical problems on the John Deere lawn tractors with these smart tips given below:

  • Let’s check the tractor’s battery first. Inspect the terminals and fuses of the battery. The terminals might be corroded or the circuits might be fused. If the terminals are mildly corroded, use a mix of baking soda and water to curb them off with a brush. If not possible, get them cleaned or replaced by a technician only.
  • Get the circuits replaced if they’re fused.
  • If the battery is too old, change it. When batteries get too old, they start losing change too fast and affect the engine’s performance.

Additional Tips To Prevent John Deere Mower Transmission Problems In Future

  • Do not leave your John Deere lawn tractor stranded for a long time. The John Deere lawn machines work to the best of their capacity when they’re used regularly.
  • Always stick to the user manual to know the correct and recommended grade of fuel.
  • To replace any part, make sure it’s the same model number as per the manual.
  • Check the oil reservoir regularly to avoid oil-contamination.
  • Along with the solutions given above, check your John Deere lawn tractor also for accumulation of debris. Always keep the lawn tractor’s deck and blades free of debris.
  • Lastly, remember to purge the mower and run the engine to burn the fuel before you store your lawn machine, to prevent cavitation from occurring.

Frequently Asked Questions

Q1. How can you fix a weak hydrostatic transmission system?

Answer – To resolve issues with the mower’s hydrostatic transmission system, change the hydraulic fuel at first. Check for trapped air in the fuel lines and if it’s present, remove it using an air compression injector. Change the drive belt if it’s broken and lubricate the pulleys well. Change the fuel pump if it’s worn-out or if it leaks hydraulic fuel.

Q2. Why do transmission systems fail on the mowers?

Answer – The hydrostatic transmission of a mower includes numerous mechanical components like the drive axle, rubber or metallic hoses, filters etc. If the hoses are broken or if the filters are clogged, the hydrostatic transmission of the mower can fail. So, replace the parts that are broken.

Q3. What is the hydrostatic transmission on a John Deere lawn tractor?

Answer – With this hydrostatic transmission system, the John Deere tractor will convert the mechanical energy into the hydraulic power which is again converted to mechanical energy. You would be using this mechanical energy to move the mower in the forward and the backward direction.

Q4. Which causes problems with the hydraulic system of the mower?

Answer – The most common issues due to which the hydraulic system of a mower performs poorly are the fuel contamination, clogging of filters, very high temperature of the hydraulic fluid and incorrect grade of hydraulic fuel used.

Q5. Is hydrostatic transmission on the mower better than automatic?

Answer – The hydrostatic transmission functions almost similarly as an automatic transmission but needs hydraulic fuel instead of drive belt to push power from the engine to the mower’s wheels. Infact, the hydrostatic transmission needs less maintenance, is more durable and works better than an automatic transmission.


Most of the time, the John Deere transmission problems occur due to negligence and poor maintenance by the users. If you understand the functioning and the basic requirements of the hydrostatic transmission on lawn machinery, you would be able to avoid most of the problems.

And for that understanding, this article will assist you thoroughly. Change the worn-out parts and keep the engine in good condition. However, if none of the suggestions work, the issue might be more serious and intricate and it’s better to get the tractor inspected at an authentic John Deere service station.

Let me know in the comments section below if you faced any other issue than the ones mentioned above. I would revert back with a solution after more research regarding the rare issue.

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John Deere Hydrostatic Transmission Problems

The John Deere hydrostatic transmission problems can be attributed to various factors, including inadequate oil in the oil-reservoir, defective mechanical parts such as hoses and brake pedals, viscous engine oil, low hydraulic fluid in the front axle, corroded battery terminals, worn-out hydraulic pump, and fuel leakage due to a deteriorated pump.

To troubleshoot these common transmission problems, several steps can be taken:

  1. Purging the Hydraulic System: Cavitation, caused by trapped air bubbles in the system, can lead to transmission problems. Purging the system can help resolve this issue. This involves a series of steps to remove trapped air from the transmission system.

  2. Checking the Hydraulic Fuel System: If purging the system does not resolve the transmission problems, inspect the fuel system for contamination and clogged filters. Additionally, check the condition of the hydraulic pump and ensure that the engine has the correct settings and viscosity of oil .

  3. Fixing Engine Issues: Engine-related problems can also affect the hydrostatic transmission system. Checking and replacing broken brake pedals, clutch cables, spark plugs, and filters, as well as ensuring the correct fuel levels, are essential steps in resolving engine-related issues.

  4. Hydraulic and Steering Fluid Change: Regular maintenance of the hydraulic fluid is crucial to prevent steering problems. Changing the hydraulic fluid at recommended intervals is important for the proper functioning of the front axle and steering system.

  5. Checking the Electrical Connections: Inspecting and maintaining the battery terminals, fuses, and circuits is essential to prevent electrical problems that can affect the transmission system.

In addition to troubleshooting, preventive measures such as regular maintenance, following the user manual for fuel grade recommendations, and keeping the lawn tractor free of debris can help prevent transmission problems in the future.

Frequently Asked Questions

  1. How to Fix a Weak Hydrostatic Transmission System: To address issues with the mower's hydrostatic transmission system, changing the hydraulic fuel, removing trapped air in the fuel lines, replacing broken drive belts, and maintaining well-lubricated pulleys are recommended.

  2. Reasons for Transmission System Failures on Mowers: The hydrostatic transmission system of a mower can fail due to broken hoses, clogged filters, and other mechanical component issues. Replacing broken parts is crucial in resolving these failures.

  3. Hydrostatic Transmission on a John Deere Lawn Tractor: The hydrostatic transmission system on a John Deere tractor converts mechanical energy into hydraulic power, which is then converted back to mechanical energy for moving the mower in forward and backward directions.

  4. Causes of Problems with the Hydraulic System of a Mower: Common issues affecting the hydraulic system include fuel contamination, clogged filters, high hydraulic fluid temperature, and the use of incorrect grade of hydraulic fuel.

  5. Comparison of Hydrostatic Transmission and Automatic Transmission on Mowers: The hydrostatic transmission, which requires hydraulic fuel, is known for its durability and low maintenance requirements, making it a favorable choice compared to automatic transmission on mowers.

In conclusion, understanding the functioning and maintenance requirements of the hydrostatic transmission system is crucial in preventing and resolving John Deere transmission problems. Regular maintenance, proper troubleshooting, and adherence to recommended maintenance intervals can help ensure the smooth operation of the lawn tractor.

Let me know if you have faced any other issues related to John Deere transmission problems, and I can provide further insights after conducting additional research.

How To Fix John Deere Hydrostatic Transmission System Problems  - Outdoor Power Equipments Troubleshooting & Buying Guide (2024)
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