Nowadays, buyers have various options when shopping for a riding lawnmower. Many models have flooded the market, and each manufacturer claims to have the best equipment.
However, hydrostatic and automatic transmission are two of the most common categories among the many riding mowers on sale. Both of these two options boast exceptional features with distinct capabilities.
So the option you choose depends on your lawn’s layout, your preference but just before that, what is the difference between hydrostatic and automatic riding lawn mowers?
In this guide, we discuss the characteristics of both hydrostatic transmission and automatic transmission, allowing you to make an informed decision on the riding mower that meets your demands.
Difference Between Hydrostatic and Automatic Riding Lawn Mowers
The main difference between hydrostatic and automatic riding mowers lies in their power supply mechanism. Hydrostatic transmission uses fluid to deliver power from the engine to the wheels, whereas automatic transmission uses belts to attain the same objective. Besides, hydrostatic riding mowers also offer more power and better acceleration than automatic riding mowers.
Are Hydrostatic Mowers Better?
Yes, hydrostatic mowers are better because you can adjust the driving speed to meet the relevant working conditions.
The hydrostatic transmissions also incorporate powerful engines with an optional cruise control function, allowing you to set the pace you want to mow your yard.
The body parts of these lawn tractors are also contrived from quality materials to enhance durability.
However, there is a cost for all these benefits as hydrostatic riding mowers are very expensive compared to their correlatives.
Hydrostatic lawn mowers also offer the best maneuverability for lawns with complicated topography. They turn around better around obstacles which saves time.
What Is the Advantage of Hydrostatic Transmission?
Hydrostatic transmission also has the following advantages besides improving maneuverability on various applications.
- Hydrostatic transmission mower works with a wide range of speed ratios. The transmission plays a critical role in handling speed such that your machine’s speed is continuously variable from zero to maximum. Continuously variable transmissions are more convenient than direct-drive transmissions, requiring you to shift the transmission to a lower ratio to increase the machine’s speed once the engine speed is maximum.
- With hydrostatic transmission, you don’t have to apply clutch and gear shifting. This assures you no disturbance in transmission.
- The hydrostatic transmission uses a single lever to adjust speed and direction.
- This transmission system has very few linkages; therefore, there is little maintenance other than annual oil and filter replacements.
- You can use the high-pressure oil from the pump to operate power steering or the dynamic braking system.
- Hydrostatic transmission has less response time than gear transmission due to fewer linkages.
- Considering that hydrostatic transmission doesn’t incorporate gear shifting, the power loss caused by friction is minimized.
What Are the Disadvantages of Hydrostatic Transmission?
Despite the many benefits of hydrostatic transmission, it also has faults. Read on for more.
A hydrostatic transmission is known to be less efficient than sliding gear transmission.
That means vehicles or riding tractors with hydrostatic transmissions subject extra load on the engine, as the machine is prone to frequent damage.
Hydrostatic transmissions are expensive to maintain because they use costly oil. Their body parts are also high-quality, adding to the cost.
Is Motor Oil the Same As Hydrostatic Oil?
Motor oil and hydrostatic oil fulfill the same functions but slightly differ in their formulation.
Motor oil contains additives that often degrade and shear down with time. These degraded additives can lead to oil foaming, comprising wear control.
Hydrostatic transmission oil is designed to fight oxidation and corrosion better than motor oil. These two attributes contribute to longer service life and improved protection during storage.
Additionally, hydrostatic transmission oil has a thicker consistency than motor oil. That tells you hydrostatic oil can withstand gear lubrication much more than motor oil, providing reliable wear protection over time.
How Do You Change Oil In a Hydrostatic Riding Lawn Mower?
The hydrostatic transmission in your lawn tractor needs servicing, including changing the filter, draining the old hydrostatic oil, and adding new oil.
Read below to learn how to change your hydrostatic riding mower oil in a few steps.
Things You Will Need
- Socket wrench
- A clean shop towel
- Torque wrench
- Oil filter wrench
- Hydrostatic transmission oil filter
- Fresh hydrostatic transmission oil
- Oil catch drain pan
Since this is a service procedure, you will need to move your lawn tractor to a flat-level working surface.
Then turn the key off, withdraw it from the ignition, wait for all moving parts to stop, and let the engine cool before proceeding.
After that, engage the parking brake to prevent your riding lawn mower from shifting gears while working.
Lift the rear of your riding lawn mower so the wheels are slightly raised, then place jack stands in two locations on the left and right sides of the mower frame.
Ensure the mower is stable before proceeding. Next, uninstall the wheel from the hub of the transaxle being serviced.
Doing this gives you enough exposure to the hydrostatic transmission oil area. Uninstall the transaxle oil filter guard from the transaxle.
Place an oil-catch drain pan below the hydrostatic transmission oil drain plug to capture the old transmission oil.
The oil drain plug is found beside the transmission mowers towards the bottom.
Some hydrostatic mowers incorporate one or more transmission oil drain plugs: one for the differential gear side, the other for the hydrostatic transmission side.
Clean all dirt and debris surrounding the hydrostatic transmission oil reservoir cap using a clean shop towel.
This is critical as it prevents the hydrostatic transmission and oiling system from contamination.
After that, loosen the hydrostatic transmission oil reservoir cap by hand to drain the transmission oil.
A loose cap permits fresh air to enter the oiling system, restricting air vacuum to enhance better oil flow drainage.
Next, unfasten the hydrostatic transmission oil drain plugs using a socket wrench to allow the transmission oil to drain completely for a few minutes.
Next, unscrew the hydrostatic transmission oil filter from the transmission oil filter housing using an oil filter wrench.
Place the oil filter wrench onto the oil filter and turn it counterclockwise to unscrew the transmission oil filter from its housing.
Install the new oil filter onto the transaxle by hand. Use your fingers to apply a thin layer of oil around the new transmission oil filter seal.
The new filter should swivel until it contacts the oil filter housing. If not, you may be cross-threading the new oil filter.
After that, finish tightening the oil filter with an oil filter wrench about ¾ of a complete turn.
Remove the fill cap from the oil expansion tank and place a funnel into the tank. Add new oil to the expansion tank until full by hand.
In the process, you will want to wait for a few minutes for the oil level to drop, then slowly add more oil until it once again fills to the top line.
As you add oil into the reservoir tank, pay close attention to the vent port beside the transaxle. If oil drips from the vent port, stop adding oil.
Tighten the vent plug with caution and wipe any residual oil with a clean rag. Since there is no torque specification for the vent plug, you will want to tighten it until you feel a stiff amount of resistance on the vent plug.
Check the oil level on the reservoir tank. If the oil level has not reached the cold fill line on the tank, add more oil until it touches that line.
Next, remove the oil funnel from the tank, wipe the remaining oil from the tank exterior and reinstall the tank cap.
Follow with removing your oil drain pan under the transaxle and returning the oil filter guard with its original hardware.
Disconnect the transaxle by pulling out the bypass lever, then set the mower to the parking brake to start the engine. After the engine ignites, release the parking brake.
Move the steering lever that controls the transaxle, which was serviced back and forth slowly around 4 to 5 times to clear air from the transaxle.
Then slide the transaxle bypassed lever in to reconnect the transaxle. After that, repeat moving the steering lever slowly back and forth 4 to 5 times.
Then stop the engine and wait for all moving components to stop and hot parts to cool. Reinstall the rear wheel and secure it with its original nuts.
You then torque the nuts to the specs inscribed in the user’s manual for your mower.
- This procedure is more intensive, so it’s best to ask your local dealer for assistance.
- It’s wise to check the hydraulic oil level when the engine is cool. That’s because hydrostatic transmission oil expands with heat, which can give you inaccurate reading when hot.
- Before starting this project for hydrostatic transmissions, read the safety instructions in the user’s manual.
What Happens If You Don’t Change the Transmission Fluid?
Transmission fluid is essential as it helps lubricate all moving parts reducing wear and tear caused by excess heat and friction.
So if you don’t change your transmission fluid frequently, it will become dirty and won’t serve as an effective lubricant.
What Are the Signs Of Low Transmission Fluid?
Checking if your mower has low transmission fluid can save you from costly repairs caused by insufficient fluid to lubricate the moving parts.
Here are some common signs that your mower needs transmission fluid:
If your transmission starts overheating, it implies that trouble is brewing. So it’s essential to keep your fluid temperature from exceeding 200 degrees since it will affect your mower’s performance.
Check out these temperatures that can damage your transmission.
- 220 degrees: varnish begins to establish on the metal parts.
- 240 degrees: the seals begin hardening.
- 260 degrees: the transmission bands begin to slip.
- 295 degrees: your mower breaks down.
Transmission fluid leakage
Another sign of low transmission fluid is leakage. You can tell if your mower transmission fluid leaks by carrying out frequent checks below the mower and the engine’s compartment.
If you notice a bright red color leaking, you will know things are not good. However, it’s even worse if it smells burnt and has a dark color.
Failing to address this leakage means more fluid will be discharged, affecting how internal components are lubricated.
Other common signs of low transmission fluid in your mower include warning lights, transmission slipping problems, and the generation of unusual sounds.
How Do Hydrostatic Lawn Mowers Work?
Hydrostatic transmissions provide high power in a compact size. This mechanism lets you mow through various speeds rather than operating with preset gear rations.
These riding mowers are powered with standard engines and incorporate hydrostatic pumps that use pressurized oil to move pistons into the hydrostatic drive system.
This piston movement delivers power to the hydrostatic transmissions, which engages the drive wheels.
Additionally, hydrostatic transmissions provide more power and improved acceleration in a smaller package.
They also have a quicker response time with unmatched maneuverability than the belt-driven lawn tractors, allowing the operator to change direction and speed quickly.
The wheel rotating speed and the truck mower speed are controlled smoothly, using the optional cruise control, according to the amount of oil delivered by the hydraulic pump.
The oil flow increases instantly by tilting the swashplate to a larger angle, speeding the lmower.
But decreasing the swashplate angle decelerates the hydrostatic transmissions without causing any mechanical wear or requiring a separate break.
When the swashplate sits neutral, the pump doesn’t deliver oil, and the mower remains stationary.
However, most users dislike these hydrostatic transmissions because they use complicated systems with additional components.
That translates to a higher price than its prevalent counterparts. Maintaining a hydrostatic riding mower is also expensive, especially if not taken care of well.
Here’s How Hydrostatic Transmissions Work In a Lawn Mower:
Can You Push Start a Hydrostatic Mower?
Hydrostatic mowers use transmissions that are fluid-driven. This permits you to steer the mower by changing the flow of hydrostatic fluid to individual wheels.
But can you push start a hydrostatic riding mower? Yes, you can push start a hydrostatic riding mower, but this causes the fluid to move backward through the pump, damaging the seals.
Therefore, you must disengage the drive before push-starting your lawn tractor.
Push-starting a hydrostatic mower only works on riding mowers with a clutch. If you don’t have a long steep hill in your yard, call a friend to help you push the mower.
This can be very dangerous, so you must use your best safety tool: common sense. Ensure nobody walks in front of the path you plan to push-start. And also, ensure no obstacles are on the way.
So assuming you have a suitable hill, push the mower to the top. You can achieve this quickly with your friend’s help.
Once you reach the hill’s peak, turn your mower to face downwards, ensuring the parking brake is engaged before turning on the ignition.
You have to implement the following steps smoothly. Begin by depressing the clutch and shifting the transmission into the lowest gear shifting.
You then hold the clutch down and release the parking brake. If your mower doesn’t immediately go down the hill, give yourself a little push with the free foot.
This should get you going. When you feel you’ve reached top speed, release the clutch. At this point, the mower should start.
If you have a friend, you will need to push the mower rather than roll it down a hill. Follow the same basic procedure and remember to pop the clutch at high speed.
Which Is Better Hydrostatic or Shuttle Shift?
Lawn tractor manufacturers are gradually upgrading and improving transmissions to make their equipment last a lifetime, become more fuel-efficient, and help users accomplish tasks efficiently.
These transmissions include power shuttle transmission, hydrostatic transmission, and geared speed transmission.
Power shuttle transmission is an upgrade to the commonly known gear-shifting transmission.
This transmission incorporates a forward-reverse shuttle lever that automatically clutches the tractor when shifted from one position, makes a shift, and re-engages the clutch.
This transmission is best if you do lots of forward and reverse gear shifting.
The clutches in power shuttle transmission machines are usually soaked in oil and hydraulically activated for long life, smooth control and lengthier transmission duration.
On the other hand, hydrostatic transmission relies on pressurized hydraulic oil to roll the rear output shaft and the wheels.
This mechanism allows you to control the speed by adjusting the hydraulic motor’s amount of oil. That said, which is better: hydrostatic or shuttle shift?
Ideally, hydrostatic is better than shuttle shift because of the super slick operation. However, this transmission system needs a high engine RPM to keep up with the transmission pump.
This causes the engine to get hot faster, burning more fuel. Also, the hydrostatic machine is costly, making a shuttle shift a better pick for those with budget constraints.
Why Is My Hydrostatic Mower Not Moving?
A hydrostatic mower may not move due to a faulty tensioner spring, low hydraulic fluid, and the rest, which we will unfold in this guide.
Drive release handle not in operating mode
Hydrostatic lawn mowers integrate a drive release for the mower to roll free. The drive release may be in the form of a knob, push/pull button, or lever.
So for you to move your mower forward, you must set these drive release handles in the operating position. You can refer to your user manual on the location of your release handle.
Low hydraulic fluid level
You must practice consistent hydraulic oil change at the intervals listed by the manufacturer for your mower transmission system to run as expected.
Running the transmission with low oil can cause your mower not to move forward or backward.
Air in the hydraulic system
After changing the hydraulic fluid, you must drive out all the air in the transmission system.
You can achieve this by keeping your mower rear tires elevated and allowing them to spin back and forth until the excessive noise disappears when the wheels run at average speeds.
Missing key in axle
If you recently replaced a tire on your hydrostatic riding mower, you may have lost a minor key that fell off the axle.
This key seems like a small narrow bar and must be installed for your lower wheel to move.
However, not all riding mowers have a key in the axle, but if yours has one and it’s not in place, your mower won’t move.
Levels operate hydrostatic mowers instead of shifting gears. So if any obstacle prevents the pedal’s forward or reverse control, your mower won’t move.
You will have to examine the pedals for obstruction or damage. If you depress the parking brake and it doesn’t release well, check for obstructions or damage to the linkage.
Also, confirm if the parking brake is engaged because this condition can prevent your hydrostatic mower from moving.
How to Check the Hydraulic Oil Level in Hydrostatic Riding Lawn Mower
It’s important to always check the hydraulic fluid level in your hydrostatic mower to ensure your equipment runs at peak performance. Use the steps below to accomplish this job.
First, place your riding mower in a service position. Then check the oil level in the expansion tanks on both sides by first removing the caps. The oil level should reach the cold fill indicator mark.
Reminder: Your riding mower’s engine should be cold when checking the engine oil level. That’s because a warm engine will give you a faulty reading.
After checking the initial oil level, carefully realign the thread to secure the cap to the extension tank.
Next, run the engine for one minute, then reconfigure your mower to service mode to recheck the hydraulic fluid level.
If your oil level is below the cold line, remove the expansion tank caps and fill the tank with fresh oil until it reaches the cold fill indicator mark.
Lastly, reinstall the expansion tank caps.
How Do You Troubleshoot a Hydrostatic Transmission?
Hydrostatic transmissions are found in various equipment ranging from lawn mowers to tractors. So for you to diagnose any problems, you need to know how the transmission system of riding mowers work.
After that, you will learn how to troubleshoot your hydrostatic mower when it breaks down. Below are some general troubleshooting tips to fix your hydrostatic mower.
Purge your hydraulic drive system
Some transmission problems are caused by air in the system, limiting the pressure needed to provide power. A quick fix to this is to follow the steps below:
First, park your mower on level ground, engage the parking brake, and elevate the rear. Ensure the oil reservoir is filled correctly according to the user’s manual.
Next, disconnect the transmission, sit on the driver’s seat, and ignite the engine. While the engine runs, move the throttle control to a slow position.
Place the motion control levers in neutral mode and disengage the brake pedal. Then push the motion control levers forward and hold for five seconds. This should purge air from the transmission system.
Check the system
Another troubleshooting tip is to check the hydraulic system visually. Check the hydraulic fluid level and add if necessary.
Examine the hoses and other connections for damage or leakage. Then clean the pump cooling fins with a clean cloth, brush, or compressed air.
You will also want to check the steering fluids and replace them if needed. Running your mower with old or overused fluid can compromise its performance.
Lastly, you can call an expert to fix any issues because some repairs are beyond DIY.
What Kind of Fluid Goes In Hydrostatic Transmission?
Due to the range of environments in which hydrostatic equipment is used, it’s not easy to give specific advice on oil types for hydrostatic transmission.
Ideally, the air temperature range in which hydrostatic equipment is used must be factored in when determining the consistency of replacement oil.
Operating outside the suggested oil air temperature range can cause premature hydrostatic transmission failure.
And for that, it’s wise to select the perfect oil for both your machine and the location. For instance, it’s advisable to use SAE 20W-50 oil in temperatures between minus 4 degrees and 122 degrees Fahrenheit.
Changing your hydraulic oil is crucial as old oil loses its anti-foam and hydraulic properties, meaning your transmission system won’t function optimally.
At worst, old oil can make your machine fail to self-propel.
As stated in his guide, both hydrostatic and automatic transmission are excellent choices for homeowners planning to improve the visual appeal of their homes.
Hydrostatic and automatic transmission comes with contemporary features that enhance your mowing experience.
Other than automatic and hydrostatic transmissions, other options to look for are electric mowers and even manual transmissions.
Electric mowers are environmentally friendly, and manual transmission offers more control as it puts you in charge of the equipment.
Even as we wind up this article, I hope you found the content helpful to your quest of understanding between hydrostatic transmission and automatic transmission.
Do you have a question, opinion, or suggestion that you would love to share regarding hydrostatic or automatic transmission? Kindly do so in the comment section below.