All John Deere Hydrostatic Transmission Problems (Solved)

You thought you’re getting a good deal on the John Deere tractor when the seller said it has hydrostatic transmission. But a few usages later, you started seeing problems. 

There are four main causes of John Deere hydrostatic transmission problems. They include faulty components, fluid leakage, coagulation nature, and worn-out transmission pump. However, the causes differ in each John Deere model.

Are you interested to learn what these problems and their solutions could be? Follow the article till the end and you’ll get your answer. 

How to Tell if Hydrostatic Transmission is Bad?

There are many ways to tell if the hydrostatic transmission is bad. If you notice the following symptoms, you can consider that the hydrostatic transmission in your tractor needs troubleshooting.

  • The John Deere tractor isn’t responding to shifting signals.
  • The transmission control arm is not working.
  • You might notice the tractor isn’t getting enough power. 
  • When the machine is in a neutral position, the tractor’s wheels are still moving.
  • The manual bypass lever got activated, and you need to push or tow the tractor. 

The main causes of these hydrostatic transmission system failures are insufficient oil, worn-out motor or pump components, faulty mechanical parts, oil leakage, and overheating engine. 

In the next segment, I’ll describe these causes in detail and teach you how to overcome JD hydrostatic transmission problems.

John Deere Hydrostatic Transmission Problems

Problem Reason Solution
Transmission slippage Malfunction of hydrostatic components. Replace the worn-out parts and fix the damages. 
Overheating problem Transmission fluid leakage Change the gaskets and the seals if they’re broken. 
Cold hydraulic system  Lack of anticoagulant in transmission fluid Add anticoagulant to the transmission fluid. 
Driving or shifting difficulty Worn-out transmission oil pump Replace the transmission oil pump with a new one.

Problem 1: Slipping Transmission System

When you notice the transmission system slip during driving, this means your tractor has a transmission issue.

The tractor will also notify you about the problem by showing an error code (P0720) on the screen. This often leads to a slow hydrostatic transmission response and gradually damages the transmission. 


The main reason for a slipping transmission is decoyed hydrostatic components. The machinery components are either corroded or worn out. Hence, the hydrostatic transmission can not function properly. 


To solve this issue, you have to replace the damaged gear solenoids with fresh ones. Fix the hydrostatic components so that they can function properly. 

Problem 2: Overheating System

The second type of hydrostatic transmission problem that can occur in your John Deere tractor is overheating. You can detect this issue by seeing an error code (P0842) on the screen. 


This kind of problem usually arises when there is a transmission fluid leakage. In such conditions, the sensors are unable to get the required pressure of the fluid. So, the transmission can’t operate properly. 


When you understand there’s a fluid leakage in your transmission, you have to inspect where the leakage has occurred.

Most of the time, you’ll find leakage around the gaskets. As soon as you detect the issue, you must fix the gaskets immediately.

But if you notice the transmission seals are worn-out or broken, you should replace the seals. This will solve your problem.

Problem 3: Hydraulic System Failure

Sometimes, you might see the hydraulic system is too cold. It’s not functioning, and the temperature sensor is signaling the low temperature of the vehicle.  


Due to cold weather, the transmission fluid thickens. So, it can’t operate the hydraulic system. This is the sole reason why it is hard to maneuver John Deere tractors in winter. 


By adding an anticoagulant to the transmission fluid, you can prevent the fluid from thickening. This will help to keep the fluid running inside the machine.

But if you notice that the low-temperature issue is more frequent than usual, you should contact a professional for an inspection.  

Problem 4: Shifting Issues

Many times, you’ll notice it’s hard to shift the gears of the John Deere tractor. This problem becomes more evident when you’re driving the tractor at a constant speed and rpm. 

John Deere Shifting Issues
Source: YouTube


This problem is the result of a damaged or worn-out transmission oil pump. As years pass, the transmission oil pump starts losing its efficiency. Hence, it creates shifting problems for the driver. 


The only fix here is changing the transmission oil pump. You should install a fresh pump that has great functioning capabilities. 

So, you’ll find these common hydrostatic problems in most John Deere vehicles. However, the problems might differ depending on the type of John Deere tractor. 

If you’re facing issues with your John Deere, go find the specific model below you’re using. In the following segments, I’ve included all types of hydrostatic transmission problems with reasons and solutions. 

John Deere 100 Series Transmission Problems

Among many John Deere models, the 100 series has a few transmission problems. Since it has a hydrostatic transmission, I’ll cover the issues and solutions in this article. 


There are 4 reasons responsible for transmission problems in the John Deere 100 series. These reasons are given below.

  • Unresponsive neutral gear.
  • Forgetting to lock the tire and axle.
  • Worn-out transmission drive belt.
  • Wrong-sized gears and transmission bearings.
  • Vibrating output shafts.

Check out the next segment to learn how to solve this issue for each of these reasons.  


If you see the neutral gear is not engaging as it’s supposed to, you have to turn off the engine immediately.

Then, move the output shaft to the left or right to unjam it. Keep rotating it in a different direction until the shaft gets completely free.

Now sometimes, you might forget to put your key to lock the tire and axle. This results in spinning wheels, but the mower doesn’t go further.

In this case, you must inspect the tire and initial setup to ensure the machine gets enough power.

If you find any worn-out transmission drive belt full of dirt and debris, you should clean it. As the machine is free from dirt, it’ll start running again.

Wrong-sized gear teeth won’t fit the transmission bearings. This makes the gear stuck and transmission failure is the consequence.

If this happens, you should call out for professional help. I usually discourage beginners from working with the gearbox and transmission system connection since it’s dangerous. 

Finally, you should check the engine vibration if the output shaft vibrates excessively. In this case, you should change the motor oil to solve this problem. 

John Deere L120 Hydrostatic Transmission Problems

The John Deere L120 tractor usually shows hydrostatic transmission problems when it’s run for more than an hour. There are a few reasons why this happens. 


The main reason for hydrostatic transmission problems in the John Deere L120 is a loose transmission. During riding the hilly areas, the transmission bolts get loosened. So, hydrostatic problems arise.

Again, an overheated engine is also another reason for transmission issues. When the engine consumes more than the required amount of oil, it misfires. Moreover, too much load on the engine also causes operational failure.  


To mitigate hydrostatic transmission issues in the JD L120, you have to take the necessary measures below:

  • First, you should check the transmission oil level. If it’s overflowing, remove the excess oil. But if there’s insufficient oil, you must add oil up to the required amount.
  • Then, check if the components are all intact or not. If you notice an internally worn-out transaxle, add 10w30 engine oil.
  • You must also inspect the drain plug associated with the transaxle. If it’s overflowed with excessive engine oil, remove the transaxle and drain the oil out immediately. 

So, that’s how you solve hydrostatic transmission problems in John Deere L120. 

John Deere D140 Hydrostatic Transmission Problems

Unfortunately, the John Deere D140 also comes with transmission problems. But they are not as many as the 100-series and L120 JD tractors. 


A broken or worn-out transmission is the culprit here, causing multiple transmission issues. It also happens when you’re using the wrong type of transmission fluid.

Because of using the wrong transmission fluid the viscosity levels don’t stay steady. Plus, it causes a transmission failure in transferring movement signals. 


So, if you detect a faulty transmission system in the John Deere D140, it’s better to replace it with a new transmission.

Also, make sure that you’re using the right transmission fluid to keep the operational flow consistent. 

John Deere LT155 Hydrostatic Transmission Problems

For John Deere LT155, the hydrostatic transmission problems are a bit different than in the other models. You’ll notice the engine stopped working only after 2 months of usage.

You can’t reverse or take the lawnmower forward. Sometimes it also shows some steering issues, and the machine doesn’t start either.


The motion issues in the John Deere LT155 usually happen because of faulty gears, bearings, and drive belts. Additionally, you’ll face starting issues due to damaged plug cables.  


To fix these issues, you must change the worn-out or damaged components and install fresh ones. This could be components like rack gear, pinion gear, driving belts, and bearings inside the machine.

You should also replace the inflaming coil in case the plug cables are wounded. If there’s still a problem, you should contact a repair center for further checkups.  

John Deere 455 Hydrostatic Transmission Problems

If you have a John Deere 455, and you see there’s a steering problem, you’ll know it’s a transmission problem. I’ve covered the reasons and solutions to all the JD 455 hydrostatic transmission problems in the next section.  


For the John Deere 455, there are only 2 reasons responsible for transmission problems. First, it happens when the transaxle starts to age and decay. Secondly, hydraulic fuel leakage can disrupt transmission operations. 


It’s pretty easy to solve the transmission issue of the John Deere 455 tractor. The first thing you have to do is check all the lock shafts and brakes. See if any part is damaged.

If there’s any sign of corrosion or damage, fix it appropriately. Then, you have to spray some degreaser on the machine. Try to keep it warm. The tractor’s ready to work again.  

How Does John Deere Hydrostatic Transmission Work?

John Deere’s hydrostatic transmission works by pressuring the hydraulic oil to travel inside the machine. Here’s a step-by-step process describing how the entire hydrostatic transmission system works:

  • The initiation of this process begins when the engine starts running. It rotates the drive shaft, which respectively turns the charge pump and the axial piston pump. 
  • As a result, the charge pump draws oil from the oil reservoir and flows it to the transmission case using an oil filter in between.
  • Then, as the transmission control lever operates, the swash plate makes the pistons rotate in and out of the piston cylinder. This helps the transmission oil to move into the axial piston motor.
  • Again, the pistons rotate the motor and push the oil inside the pump. It’s also connected to the output shaft. 
  • Finally, the oil starts turning the large bull gear in the differential. Consequently, the rear wheels get power and help the vehicle to move. 

  Any misstep in this process can lead to transmission failure.


How often do you change the oil in a hydrostatic transmission?

Usually, you should change the hydrostatic transmission oil every 50 hours of usage in old tractors. In the latest models, you have to change it after the first 75 hours of usage. Then, you should change it every 400 hours. It depends on each type of tractor and its capacity.  

How long do hydrostatic transmissions last in tractors?

Hydrostatic transmissions last for about 500 hours in tractors. However, the timeline can change depending on various factors such as the frequency of tractor usage, load capacity, type of tractor, and type of usage. 

How reliable are hydrostatic transmissions?

Hydrostatic transmissions are extremely reliable. They can give you precise action and steering in small areas. It’s also easy to handle and use. You don’t even need to operate the loader with your hands all the time. 

Which is better: hydrostatic or automatic transmission?

The hydrostatic transmission is better than the automatic transmission. They provide a smooth riding experience and require less maintenance. But you must be careful about adjusting the mower every once in a while since hydrostatic transmission is sensitive in usage.  

Final Words

So, these are the John Deere hydrostatic transmission problems you might encounter using the models mentioned in the article.

Well, no matter which tractor you’re using, you should invest in frequent maintenance. This will help keep the tractor running smoothly and free from any issues. 

Best of luck!

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