It can be discouraging when your lawn mower stops moving and you don’t know what to do. The most likely cause of a moving problem on a riding mower is the hydrostatic drive system.
A hydrostatic riding lawn mower won’t move forward or reverse due to a bad drive belt; bad tensioner pulley; broken tensioner spring; old, low, or hot hydraulic fluid; air in the hydraulic system; or the drive release lever in the bypass position.
I’ll share with you items to check in your hydraulic system along with some non-hydraulic system-related items that may affect the engine causing the mower to die and stop moving.
Remove the spark plug wires and ignition key before starting repairs. Follow all safety precautions found in your operator’s manual.
This post may include affiliate links. Purchases made through these links may provide a commission for us, at no extra cost to you. As an Amazon Associate, we earn from qualifying purchases.
Follow all safety instructions provided in your equipment operator’s manual before diagnosing, repairing, or operating. Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.
More articles that may help with your riding mower driving problem:
- This is Why a Zero Turn Mower Won’t Move Forward or Reverse
- Troubleshoot Common Riding Mower Problems
Reasons a Hydrostatic Riding Mower Won’t Move Forward or Reverse
Drive Release Handle Not in Operating Position
Hydrostatic riding mowers have a drive release so the mower can free-roll. This is especially helpful when your mower has stopped working and you need to push the zero turn onto a trailer.
In order to be able to move the mower forward or reverse, you must have these drive release handles in the “operating” position.
The drive release can be in the form of a lever, push/pull button, or knob. Refer to your owner’s manual for the type of handle you have on your mower and where to locate it.
Missing Key in Axle
If you have recently changed your tire on a riding lawn mower, you may have missed a small key that fell out of the axle. This key appears to be a small narrow bar and must be installed in order for the wheel to move.
Not every mower has a key in the axle, but if yours does and it isn’t replaced, the mower won’t move.
Mower Drive Belt is Worn, Loose, or Broken
Check your mower drive belt to make sure it hasn’t fallen off and is positioned correctly on the pulleys. If the belt appears worn, cracked, or broken, you must replace the drive belt.
Bad Tensioner Pulley
Tensioner Pulleys are often made from hard plastic with a bearing in the center. The pulley can break or the bearing can fail. Check your pulley and replace it if necessary.
Keep the tensioner arm greased so it has some movement and does not seize up. Without proper tension on the belt, the mower won’t go forward or reverse.
Missing Idler Arm Spring
The idler spring places tension on the drive belt. Replace the spring if it is broken or has fallen out of your mower and is now missing.
Low Hydraulic Fluid Level
A consistent hydraulic oil change at the intervals recommended by your manufacturer must be completed to keep your lawn mower transmission system running at its best.
Your mower won’t move forward or backward when running the transmission with old hydraulic oil or low hydraulic oil. If it does move, it may seem very weak while moving.
Again, change your hydraulic oil and filter(s) at the recommended intervals. Don’t forget many manufacturers have a “break-in” period when you are changing your hydro oil a little sooner for the initial oil change.
When your hydraulic oil is low, add more hydro oil until the fluid level reaches the full level when your hydraulic oil is cool. It’s also a good idea to check for hydraulic fluid leaks.
Note: some entry-level zero turns will have “non-serviceable” transmissions which means the hydraulic systems are sealed and you are not able to change your hydraulic fluid. If you are having hydraulic issues, bring your mower into your servicing mower dealership for assistance.
Bad or Hot Hydraulic Fluid
When you operate your lawn mower with bad hydraulic fluid or low fluid, the oil is not able to efficiently lubricate the hydraulic system causing increased friction and overheating of the hydraulic fluid.
Hot hydraulic fluid can also result in more extensive damage.
I highly recommend taking your lawn mower into your local repair dealership if you experience leaking from your hydraulic pump or your mower runs fine when it is cold, but stops running when it gets hot.
Air in the Hydraulic System
After changing hydraulic fluid, you must bleed all of the air out of the system. Air in the system can prevent your mower from moving.
Air can be removed from the system in most lawn mowers by raising the rear drive tires off of the ground and allowing them to spin forward and in reverse until you don’t hear excessive noise while the wheels move at normal speeds.
It is important to refer to your operator’s manual for correct procedures to remove air from your model lawn mower’s hydraulic system.
Procedures not only can change from manufacturer to manufacturer but also from model to model.
Non-Hydraulic Related Items that Can Keep Your Mower from Moving Forward or Reverse
If you don’t find the fault of your moving problems in your hydraulic system, you can check other items that can prevent the fuel and air required to run your engine.
Definitely check out these items if your engine starts to sputter or shuts off so you are no longer able to drive.
- Battery and Charging System
- Clogged Fuel Filter and Fuel Lines
- Clogged Air Filter
- Dirty Carburetor
To read more about items that can result in your mower stopping while mowing and how to fix them read my article “Reason Your Mower Stopped While Mowing”.
Still Having Problems with Your Lawn Mower?
Lawn mower ownership doesn’t come without its frustrations. Own a mower long enough, you are bound to run into many lawn mower problems including starting, smoking, leaking, cutting, and overheating.
For mower troubleshooting, check out my guide Common Lawn Mower Problems: Solved.
A riding mower won’t move forward due to a worn drive belt, worn tensioner spring, bad pulley, air in the transmission system, or hot, old, or low hydraulic oil.
A riding mower won’t drive when the transmission bypass lever is not in the drive position, the brake is engaged, the axle key is missing, air is trapped in the hydraulic system, or the hydraulic oil is low, hot, or old.