When you’ve left your mower out in the yard, it can tempting to just try and push it back into the garage without starting it up again. However, trying to do this the wrong way with certain types of mowers – such as those with hydrostatic motors – could do lasting damage.
You can’t push hydrostatic mowers without disengaging the transmission. Fluid is pumped to the wheels to turn them, so if the motor is off the pump is too and the wheels won’t turn. If you push the mower when it’s off, the fluid already at the wheels will flow back into the pump and damage it.
With that said, let’s dive down into what a hydrostatic mower actually is, how they work and why pushing them when the engine is off is a bad idea. We’ll then compare hydrostatic engines to other popular types of motors.
How Do Hydrostatic Lawn Mowers Work?
Choosing a lawn mower is hard. There are a lot of choices. If you decide you are in the market for a riding lawn mower, then you will have to choose a transmission.
We all know that cars can have manual transmissions or automatic ones. Those are options for riding lawn mowers as well. In addition, riding lawn mower manufacturers have added one more transmission – hydrostatic.
Transmissions transfer power from the engine to the wheels, and they manage the vehicle’s speed. Experts recommend you choose your riding lawn mower transmission type based on your lawn topography, how often you mow and your driving habits.
Is a hydrostatic mower a good choice for you? Do you have a lot of sharp turns to make? Do you live in a damp climate where the grass is often a little wet? Do you have steep hills? Does your lawn have lots of flower beds and trees to dodge?
Do you think you’d use cruise control? Are you bored with slow mowers? If the answer to any of these questions is yes, you should consider a hydrostatic mower.
Here’s a handy resource that explains most of the choices.
Hydrostatic motors are not new – they were invented in 1965. Most modern tractors have them. In hydrostatic mowers, there are no shifting levers or clutches. Gear changes are smooth and fast. Hydrostatic mowers have power and torque – they won’t leave you stuck on a steep hill.
Hydrostatic riding lawn mowers (HST’s, hydros, or hydro-drives) are a lot like an automatic car, but instead of a series of belts that turn the axle mechanically, they use fluids. Powered by a standard engine, a hydrostatic pump moves pressurized oil into the hydrostatic drive system.
The oil moves the pistons, which power the hydrostatic motors. The hydrostatic motor engages the drive wheels.
Many hydrostatic mowers are riding lawn mowers, but you can have a hydrostatic walk-behind as well.
For all you hydrostatic transmission enthusiasts, here’s a video. Geek your heart out!!
Why You Can’t Push a Hydrostatic Mower
Your hydro mower is your baby. Your workhorse. What happens when it stops running? Or you just need to move it a few feet in the shed? You push it, but it’s heavy and hard to move.
Stop! Stop right now!
In a hydro mower, fluid is pumped to the wheels to get them to turn. If the motor is off, the pump won’t pump, and the wheels won’t turn. If you turn the wheels by pushing on the mower while the motor is off, you can cause the fluid that’s already at the wheels to flow backward, into the pump. Fluid flowing backwards into the pump will damage it.
If you need to push your baby to another spot, don’t panic – there is a simple mechanism to disengage the hydro drive so you can push it around safely. This mechanism is called the disconnect or – neutral, manual bypass or transmission release lever.
Check out your mower’s manual or watch some manufacturer videos and find out where your mower’s disengage lever is. It could be a lever, a shaft, pulley, axle or a knob. If you have a four-wheel drive mower, or zero-turns (ZTR’s) there may be two levers to find.
On many mowers, the levers are at the back and you simply pull them out to disengage the drive. On others, the lever pushes in. If you have a grass collector, chances are you’ll have to take it off to find the lever. On some mowers the lever is down by the axle and for some it’s under the seat.
Here’s a video showing lots of different mowers and where their disconnect levers are located.
How To Push a Hydrostatic Mower (Simple Steps)
Follow these steps to safely push your hydrostatic mower when it’s turned off, and you won’t damage the pump or engine:
- Read the mower instructions or watch videos until you can locate the disconnect lever(s) on your mower.
- Take a minute to plan your strategy. Consider what will happen when you disengage the drive. Got hills? Steep hills? Plan out how you are going to control the mower because once you disconnect the drive, and let off the hand brake, the (heavy) mower will be freewheeling. Down the steep hill.
- Turn off the engine and remove the key.
- Set the parking or hand brake.
- Go to the disconnect lever. Take a look (or take a photo) of the current position of the disconnect lever, because you will be returning the lever to that position after you are done.
- Push, pull or turn the lever(s) or knob to disconnect the hydro drive.
- Release the hand brake.
- Push the machine to its new home. It will be a little hard to push because of hydraulic drag.
- Set the parking brake.
- Reconnect or re engage the hydro transmission lever.
What is The Advantage of Hydrostatic Transmission?
The advantages are control, power, and simplicity. Hydrostatic mowers are the most high-powered of all transmissions. They change gears the smoothest. These transmissions last the longest (with some routine maintenance).
There are no gear levers to operate. No clutches. For lawns with a steep slope, hydrostatic mowers have an advantage: they have greater torque than other mowers.
Hydrostatic mowers offer the best acceleration and maneuverability. For lawns with complicated topography, they change gears faster and smoother. They turn around better – which saves time. If you have a large yard with several flower beds and trees to dodge, consider a hydro mower.
If you think mowing the lawn is a boring chore, consider a hydro mower. Maybe you need a mower with pizzazz. Reviewers call hydro mowers “fun” and “like a go-kart”. In fact, hydro mowers can get away from some drivers, so be careful. They have the power to accelerate – and decelerate – quickly.
Hydrostatic transmissions are fluid-filled – there’s minimal wear from friction. With simple maintenance, they last longer than other transmissions. Hydro mowers need routine fluid level checking.
Check your manual, but most experts recommend using 20W50 motor oil – not hydraulic oil. They recommend that you change the oil when the mower is new, within the first 50 hours of usage. Then, every 250 hours or once a year.
For all these benefits, there is a cost – hydrostatic mowers are the most expensive. They also need more fuel and maintenance. Routinely check oil levels.
Hydrostatic Vs Hydraulic Mower Transmission
The transmission types hydrostatic and hydraulic have something in common: “hydro” or liquid. Both transmissions work because of basic fluid properties: liquids won’t compress, they have no shape, and they exert equal force to all perpendicular surfaces.
Hydrostatic and hydraulic transmissions require a pump – and the pumps for each system are different. In a hydraulic system, the pump moves a fixed amount of fluid in one direction. In a hydrostatic system, the pump (called a variable displacement pump) is capable of moving liquids in two directions and can move variable amounts.
So in the final analysis, you can safely push a hydrostatic mower without damaging the pump or motor if you follow the simple steps outlined in this article.
As a teenager I remember trying to push our riding lawn mower once when it was switched off, and it wouldn’t budge an inch. My old man came out and went crazy and then told me about the transmission thing – so I learned this the hard way! Hopefully this article will help you avoid the mistake I made, and ensure your hydrostatic mower has a long and well-maintained grass cutting life 🙂