How to Disengage Hydrostatic Transmission (Essential Information)

Today you are going to read the complete How to Disengage Hydrostatic Transmission (Essential Information). Regular maintenance is very significant for any lawnmower, machines, devices, vehicles and others as well. However, even if you never missed your maintenance schedule, sometimes they’re just acting up with no solid reason.

If it involves something in the machine that is complicated such as a hydrostatic transmission system, we might blur what to do.

To start, let us read some facts about hydrostatic transmission in case you have no idea about it.

What is Hydrostatic Transmission?

Hydrostatic transmissions are used or applied in many applications such as vehicles, mobile equipment, lawnmowers and others. The hydrostatic transmission is also known as hydrostatic drive.

Engines, such as those found in most cars or zero-turn mowers, transfer power to the axle, which turns the wheels. In detail, the power is transferred from the engine to hydraulic pumps, which move the wheels using liquid pressure.

The power actually is transferred using a hydrostatic transmission. There are no gears required, and changing speeds is quick and easy. In short, hydrostatic transmission makes the process efficient.

As hydrostatic transmission involves so many components which are located on or inside the hydrostatic pump, it is one of the hardest systems to understand.


Okay, moving on. Hydrostatic transmissions, in general, employ pressurized oil to produce movement for the tractor or mower. A pump inside the gearbox pressurizes the fluid (oil). Problems with zero-turn hydrostatic transmission are commonly caused by the presence of air in the system.

This phenomenon is known as cavitation, which is harmful to the pump since it allows the pump to run dry. When the pump is full of air rather than fluid (oil), it cannot create the pressure required to deliver the power, and therefore the transmission is unable to provide the required movement.

This is a very typical occurrence with zero-turn mower engines. If your mower is brand new or has been kept for a long period (more than 2 months), the transmission must be purged or disengaged before use. It’s also an excellent point to start if your device is making a sound or has a slow movement.

How To Disengage How to Disengage Hydrostatic Transmission?

It is critical to disengage the hydrostatic transmission or to reset the engine to a default condition to allow the vehicle to move freely and effectively.

The transmission can be removed using levers or other hardware similar to it, in order to open the bypass valve in a How to Disengage Hydrostatic Transmission.

To discover how to accomplish it, follow the instructions below. Check it out!

  1. To begin, secure the back of the mower to jack stands on a level surface, turn off the engine, and engage the parking brake. Always remember that safety comes first.
  2. After that, disengage the transmission by setting the freewheel control to the “freewheeling” position. Before beginning the purge/disengaging process, the oil reservoir must be filled to the requirements specified as stated in the device handbook (as the requirement may be varied based on the types of devices).
  3. There are several mechanical components such as a differential and an axle as well as rubber or metal tubes that involve pumping liquid through, in a hydrostatic transmission. Hydrostatic transmission issues can be caused by the failure of these mechanical components, such as a leaking hose or a clogged filter.
  4. However, the oil itself, though, will be the most common concern. It is important to note that the temperature has an effect on the oil viscosity, so a suitable oil is important to make sure it is sufficient for the device to run intolerable weather.
  5. Next, try to start the engine. After the engine has started, set the throttle control to the slow position. Slowly release the clutch/brake pedal while keeping the motion control levers in the neutral (N) position.
  6. Hold the motion control levers in the fully forward position for five (5) seconds. Then, vice versa. (Hold the levers in the reverse position for five (5) seconds). Repeat this step three times. The drive wheels may move slightly throughout this process. The hydraulic drive system’s air is being purged.
  7. After that, set the motion control levers to neutral (N) again. Turn off the engine and engage the brake. Inspect and replenish the oil as needed.
  8. Close the bypass valves on the pumps to engage the transmission or place the freewheel control in the drive position.
  9. Start the engine again. This time, set the throttle control to maximum speed (in step 3, it is set in a slow position). Slowly release the clutch/brake pedal while keeping the motion control levers in the neutral (N) position.
  10. Try to move the motion control levers slowly in a forward direction then reverse it back after moving forward around 5 feet. And then, set it back to the neutral (N) position. Repeat it three times.
  11. Your mower now has been completely disengaged/purged of the How to Disengage Hydrostatic Transmission. You can use it normally with efficient performance right away.

Troubleshooting Hydrostatic Issues

If you have done all steps above and the hydrostatic transmission is already disengaged, but your mower/device still has an issue, then you really need to do a few extra steps in order to solve the issue.

  1. System assessment: Begin with a thorough examination of the hydraulic system’s components;
  • Ensure that the oil level is enough and, if necessary, add more.
  • Check for any damage or leaks in the hoses and connectors, if any.
  • Check the pump cooling fins in case it has any damage and clean it.
  1. Replace the fluids in your hydraulics and steering: Fluids that are overused or not suitable are the most common cause of slow performance. If there is no evidence of fluid leaks or damage, it is possible that it is time to replace it (hydraulic and steering fluids).
  2. Ask help from an expert: Contact your dealer if you need assistance troubleshooting your mower/device’s hydraulic system. Don’t be afraid to call in an expert when the time comes. This will help you save a lot of time and money, honestly.


How to Disengage Hydrostatic Transmission actually offers a smoother and efficient ride, plus does not need intensive maintenance.

However, you need to disengage it if it does function properly (the oil is replaced by the presence of air) before engaging it back to improve your mower or device performance.

You just need to follow the simplified steps above to do it, then you are on the right track. No worry, if you are a beginner we are pretty sure you can do it also.

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Good luck!