John Deere Won’t Move Forward or Reverse? Fix Mower Problems


If your John Deere riding mower won’t go forward or reverse, chances are, it’s a mechanical or software issue. In addition, if your mower won’t move, the issue might be Transmission failure. For example, in 2015 and 2017, John Deere recalled models for high likelihood of transmission failure. Many people also report specific transmission issues with the John Deere 8300, 314, and la 120. 

If your John Deere mower won’t go forward or reverse, it’s a good idea to run the transmission calibration. In addition, many small John Deere mowers have switched to hydrostatic transmissions. You may have to check basics like oil, line clogs, etc., before proceeding. 

3 Issues Which Affect JD Mower Forward and Reverse Movement 

If your JD lawn mower won’t go forward, it’s likely to be one of a few easily diagnosable issues. However, your first step should always be to check the PCU for fault codes. This can simply tell you what’s going on. 

Quick Tip: Check the transmission bypass “neutral valve”. This lever is designed to bypass the transmission controls so you can manually move your hydrostatic mower. If it’s pulled out, your John Deere mower won’t move with power on. It’s almost always in the back and looks like an Allen Wrench. However, placement varies based on mower. 

1. Transmission Failure 

Transmission failure is the most likely reason your lawn mower won’t go forward. That’s especially true if you have a newer hydrostatic transmission rather than an older gear transmission. Why? Hydrostatic transmissions are easier to operate, but if you don’t maintain them with top-ups, they will fail. In addition, transmission problems in JD riding and zero turn mowers are common. For example, John Deere 8300 transmission problems are reported constantly. In addition, John Deere recalled 25,000+ tractors in 2017, following potential transmission failure. If you have a D105 tractor, you may want to have it checked. 

First, make sure you have your mower manual at hand. If not, download a copy from John Deere’s website here

Inability to Shift Gears

If your John Deere is starting up but won’t move, it’s likely that the issue is the gears. If you have a hydrostatic transmission, low fluid levels will cause the gear to slip out of place. Then, your JD won’t move forward or backwards. What now? Do a basic troubleshoot to assess likely causes of the issue. 

  • Check fluid levels. Top up with appropriate fluid for your transmission. Your mower manual has a section on appropriate fluids for your specific mower. There are specific instructions on how to check and change the fluid in your manual. Make sure you follow them. 
  • Most JD transmissions require a fluid change every 400 hours after the initial 3-month break-in period. You can do this yourself, however, oil service depends on your mower, so check the manual. 
  • Once you’ve ensured the fluid levels are good, run the transmission calibration cycle. Your John Deere manual has specific recommendations for your transmission. In most cases, calibration should be annual to every 3 months depending on volume of use. Failing to calibrate can actually cause transmission issues and gear slippage. 
  • Check the PCU fault codes. If the light is flashing, it’s sharing a code. This relates to machine part failure. Refer to the manual for the fault code. If the fault code isn’t in your manual, it’s likely a PCU board failure or issue. 
  • Check the armrest control board. Simple issues like loose screws on the control board can cause the gears to have problems. This is especially common on power shift transmissions like the 8400. 
  • Check for mechanical failure in the gears, such as worn teeth, broken teeth, or other damage which could cause slippage and jams. 

Leaks in the Fluid Reservoir or Transmission Lines

If you’re topping up fluid often enough but still seeing gear slippage, you might have leaks in the fluid reservoir or in the transmission lines. You also might have kinks or breaks in the lines, which might reduce fluid flow through the machine. 

  • Check fluid levels in the machine. Most John Deere mowers now have a sight glass with level markings. However, you may also have a dipstick. Make sure you follow the manual instructions and run the engine at 1000 RPM for at least 1 minute, turn the engine off, and allow the fluid to cool for at least 3 minutes before checking the fluid. Importantly, you cannot get an appropriate read with the engine on. 
  • Turn the mower on and allow it to Idle for 10-15 minutes. Check if there are spots or marks under the mower. 
  • Remove the seat and back cover from your machine.
  • Move the gas tank.
  • Check for grease buildup on and around the fluid lines. This is indicative of a leak. 
  • Look for kinks, broken or twisted lines, or other signs of damage such as punctures.
  • Double check the fluid reservoir for the same.

If you have breaks or leaks in the lines, it’s a good idea to replace them. Costs vary, but often you can replace a John Deere fluid reservoir for $50-$100 and lines for about the same. 

Mechanical Failure

Modern John Deere mowers have a PCU controller in place to assess engine health and part failure. In this case, the light should be flashing. However, the PCU controller is a part that commonly fails. That’s especially true as the controls are normally built into the arm rest, where they can take considerable jostling and jolting during normal use. If you don’t have a PCU code flashing, it’s always an idea to take your JD mower in for servicing. Alternatively, you can try checking the PCU controller for loose screws and wires. You can do this by taking the armrest controller apart. However, if you turn your transmission on and the pulley is spinning but the wheels aren’t turning, you might need a new transmission or a new mower. 

Unfortunately, any single part on a transmission can fail. This might be replaceable. It might not. If your PCU fault codes don’t tell you what’s going on, it’s a good idea to get it serviced. 

Clutch Issues 

Clutch issues can cause gear and transmission part issues. If you think your transmission is fine, it’s always a good idea to check the clutch. This includes recalibrating the clutch, checking PCU codes, or physically inspecting the clutch. If the clutches are broke, the cable is damages, or the pulley system is broken, your John Deere mower won’t move

Most John Deere mowers have a basic electric PTO clutch. You can take it out and:

  • Check resistance. You want between 2 and 4 Ohms of resistance. Use a battery powered meter. 
  • Hook the clutch to a 12-volt battery from the mower to ensure the clutch works.

2. Clogged Fuel or Air Filters or Carburetor Issues 

The second step should be to check charge pressure and system pressure. If they are low or below PSI, you probably have a fuel or air filter or valve problem. This check is relatively simple because if pressure is as expected, the filters and valves are probably fine. However, you can manually inspect the valves anyway. Unfortunately, placement varies depending on which John Deere mower you have. 

First, check the wheeling valve to ensure it isn’t turned off. This knob is almost always in front of the seat. If it’s turned off, it turns off the check valves. Checking that it’s turned all the way on is the easiest potential fix. 

  • Check charge pressure.
  • Inspect the filter.
  • If the filter is clogged, replace it.
  • Check the Charge relief valve. If it’s defective or clogged, replace it or clean it out.
  • Check the implement relief valve, if it’s defective or clogged, clean or replace it.
  • Inspect the charge pump, if it’s defective, repair or replace it.
  • Check that the relief valve pins pop up when the motor starts.
  • Check PSI requirements in your manual to see at what pressure level the machine goes into bypass. For example, the 4300 goes into bypass at 6000 PSI. If you exceed that, your mower won’t move forward. 

Grass and dirt frequently build up in mower engines. It’s always a good idea to do a regular check to clear these out. And, if your air filter is damaged or looking worse for the wear, it’s always a good idea to just replace it. 

You’ll also want to check the carburetor. Here, the carburetor mixes air and fuel together to enable internal combustion. If your carburetor is having issues, engine performance might drop enough that your engine refuses to move the mower. However, this type of failure is unlikely so it should be in one of the later things you check. 

3. Issues with the Battery 

John Deere mowers use a 12-volt battery to power up the starter and to run the electronic control panel and diagnostics. If the battery is dead, there are loose wires, or other issues are in place, your mower might start but not move. This is especially likely if your mower stalls and sputters if you leave it idling. 

However, the easiest check is to use a voltmeter. 

  • Set the voltmeter to 13 using a DC or “A” test. 
  • Position the leads on the +/- posts and check the reading. 
  • Here, any charge between 12.4 and 12.9 is an indicator your battery is properly charged. If it’s under 10.5, you want to replace the battery. 

Avoid Future Front and Back Gear Issues

If your riding lawn mower won’t go into gear, chances are, it’s a maintenance issue. This often means you can easily prevent future issues with good maintenance. 

Keep Up with Fluid 

Most John Deere mowers require fluid changes every 400-500 hours of operation. That’s a long time for a home-use machine. Therefore, fluid might run low well before that time. It’s always a good idea to check fluid levels every 3-6 months depending on how often you use the mower. 

Regularly Clean Your Mower

Lawn mowers easily become clogged. That’s a natural fact of running a mower with blades and a motor on the bottom of the vehicle. In most cases, you’ll want to inspect and clean your mower every 3-6 months to remove built-up grass, debris, and grease from the airlines, the motor, and the transmission. For example, even a small amount of grass in the filters can cause failure. 

Calibrate the Transmission 

It’s important to calibrate the transmission occasionally. However, the frequency at which you should do so is listed in your manual. This applies even if you have a power shift transmission. In most cases, a yearly calibration is always a good idea. For example, if your lawn mower won’t move forward or backwards, it might be a simple calibration issue causing back or forward gears to slip. 

Check PCU Codes as They Appear 

If your engine diagnostics is flashing, you should always check the code immediately. PCU codes can warn you of potential upcoming faults, with enough time to replace or fix the part to prevent a more serious problem. Staying on top of maintenance will increase the longevity of your mower. 

Inspect the Mower Regularly 

It’s always a good idea to manually inspect your mower to look for oddities. For example, does your mower have loose screws? Is the drive shaft still firmly attached to the transmission? Are there grease or fluid spots from leaks? Are there blockages? Is the center control loose? Are there loose parts in the motor? Lawn mower motors are low to the ground, which means they are jostled quite a bit as you drive around. The more you use the mower, the more likely it is that something goes wrong. 

DIY Or Call a Pro? 

If you’re experiencing significant problems with your mower, it’s almost always better to call a professional. Why? If you were experienced enough with replacing parts to do so, you’d probably skip this question. However, it’s always a good idea to do a basic troubleshoot, to refer to your manual, and to see if you can resolve the issue that way. 

For example, it would be a shame to pay for a professional checkup if your only issue is the neutral valve has been pulled out. On the other hand, if you have part failure in your transmission, you might not have the expertise to validate that yourself. 

Cost to Fix John Deere Riding Mower – Most riding mower repair services have fixed rate prices for servicing, service and repair, and pickup. For example, you can expect to pay about $200-$300 for a tune-up across the country. Mower pickup will vary significantly depending on distance. And, parts are always an important part of costs, as replacement transmission parts can be expensive. In most cases, you can also expect to pay $40-$75 in garage fees, plus an average of $25 per day the mower is there. Labor normally varies between $30 and $60 an hour. Finally, pricing is determined on the complexity of the problem and the cost of the parts. 

Our tip is to run through the troubleshooting, go through the manual, and if you can’t find and resolve the issue, take your mower to a professional. 

Frequently Asked Questions

If you still have questions, this FAQ might help. Otherwise, you can call your local repair technician or your mower dealer. 

How long do lawn tractor hydrostatic transmissions last?

It’s difficult to measure the life of a hydrostatic transmission. However, some estimates expect that bearings will start to go out after 5,000 hours of usage. On the other hand, if you don’t replace or top up fluid often enough, that failure could come much more quickly. So, the lifespan of a hydrostatic transmission is heavily dependent on maintenance. 

How much does it cost to service a John Deere riding mower? 

In most cases you can expect to pay $80-$1200+ for servicing a John Deere riding mower. Here, costs depend on the complexity of the diagnostics and the fix, the cost of the part, and the duration of time in the garage. 

How long does a lawn mower last? 

A well-maintained riding mower can last well over 10,000 hours of usage. However, this requires good maintenance. In most cases, you can expect closer to 5,000 hours, simply because most people don’t put in the maintenance required for better longevity. 

To End

If your mower will not go forward or reverse, it’s a good idea to check basics like the neutral valve setting, the flywheel, and the battery. Afterwards, you can troubleshoot the transmission, the battery, and the intake. Hopefully, you can find an easy fix for your lawnmower there.

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