There is little more frustrating than an issue with your Husqvarna lawn tractor’s hydrostatic drive transmission.
Luckily, we’re here to help.
In our thorough guide, we’ll highlight some of the five most common problems and their respective fixes, from air in the lines to fluid leaks.
Some of the most common reasons for Husqvarna hydrostatic drive transmission problems include issues shifting the mower into gear; a hydraulic fluid leak; air in your mower’s lines; the lawn mower isn’t starting due to anything from old or bad fuel to faulty spark plugs; or the mower isn’t moving forward or backward due to anything from a missing axle key to trapped air.
Why Should You Be Worried About Your Husqvarna Hydrostatic Drive Transmission?
If your Husqvarna isn’t performing as it should, or you suspect its hydrostatic drive is malfunctioning, you should be concerned.
A hydrostatic drive (you might also hear it called hydro-drives, hydros, or HSTs) is a hydraulic system. The hydraulic pump helps your motor work effectively by using fluid that travels through bendable hoses. With a hydrostatic drive transmission, your lawnmower doesn’t need gears to convert the rotating mechanical energy from source to source.
If any of the components fail here (or if there are any leaks), your mower won’t be moving anywhere any time soon.
A hydrostatic drive transmission that’s malfunctioning is certainly cause for concern, and ignoring these issues can hurt your mower in the long run.
Husqvarna Hydrostatic Drive Transmission Problems (and Fixes)
If your Husqvarna hydrostatic drive transmission isn’t working properly, you’ll want to fix it as soon as possible. But there are a few causes that can lead to issues with your hydro-drive transmission that you should know about.
From hydraulic fuel leaks to air in the lines or even a mower that doesn’t respond to shifting, we’ll cover these topics and more (along with their respective fixes).
Problem #1. Your mower doesn’t respond to the shifting.
Your lawnmower might not seem as powerful as it once was. Or maybe, it truly doesn’t respond to shifting.
This isn’t exactly unheard of. Actually, it’s a pretty common problem. Not responding to your shifting can happen if the mower’s hydrostatic drive transmission control arm is out of adjustment. You’ll most likely notice the mower’s shifting difficulties while driving. It could also completely fail to shift.
Although the Husqvarna lawn mower’s hydrostatic drive transmission oil pump is known to be dependable, these pumps can occasionally become less efficient early in its lifetime. They’ll have trouble building pressure fast enough and will begin to break down as it gets older. Due to this issue, the shifting performance of the mower will be affected.
You’ll know it’s time to find and adjust the adjustment bolt if the lawn mower’s wheels keep moving while it’s in neutral.
If the mower doesn’t respond when you shift the control arm, you can activate the manual bypass lever.
Before you do so, make sure your parking brake isn’t on. If you try to shift the mower without releasing the parking brake, it won’t respond — that is, it’s not going to move backward or forward. Make sure you disengage the cruise control before attempting to shift, always.
However, it could also be due to a worn-out transmission oil pump. Replacing this can totally solve your problem. Oil pumps can also be taken out and reconstructed to fix the issue.
Problem #2. You’ve got a hydraulic fuel leak.
The Husqvarna lawn tractor’s hydrostatic drive transmission is pretty advanced. They have leak-proof systems, so if anything is leaking out of them, it could be a catalyst for an overheated transmission.
As such, it’s possible that your Husqvarna mower’s movement could be crippled by a hydraulic fuel leak, the oil that powers the hydraulic pump.
You can know whether or not there’s a leak issue by taking note of any possible signs and symptoms, including:
- A burning smell
- A lack of optimum pressure in the lines
- An error, such as “P0842” or other errors in the same or similar range that are linked to transmission fluid pressure
- Your mower isn’t running smoothly overall
To fix a hydraulic fluid leak on your Husqvarna, you’ll need to change the lines (if you’ve found the leak). You’ll need to replace them when the rubber parts crack or become worn down, as the oil can leak out of the seal.
Due to the immense pressure, the engine’s central component, the crankcase, can also crack or break. If that’s the case, you’ll need to replace that part in order to stop the leak.
So, you’ll need to find the leak’s location and close it before it causes any significant or irreparable damage to the mower.
Typically, a fluid leak is caused by worn-out transmission seals or because the gaskets are worn out or broken.
Problem #3. There’s air in the lines of your mower.
If your lawn mower is idle during autumn or winter, air can get into the lines. Because of this, there’s not enough pressure for your mower to work like normal. To fix it, you’ll need to remove the air from the mower’s lines.
To flush air out of the lines, try the following steps:
- Lock the mower’s rear wheels with objects to set the lawn mower in place.
- Put on the parking brake.
- According to the Husqvarna owner’s manual, disengage the transmission.
- Once you turn on your mower, shift it into neutral and release the brakes.
- For about five seconds, push the throttle all the way forward.
- After waiting five seconds in your mower’s forward position, put the throttle in reverse. Keep it there for another five seconds, give or take.
- Repeat this same process a series of three times. This should force the air out from the hydrostatic drive transmission.
- Turn off your lawn mower.
- Re-engage the Husqvarna’s hydrostatic drive transmission.
- Drive the mower forward for around five seconds after the transmission is re-engaged. Afterward, do the same process but in reverse.
Hopefully, these steps should expel the air from the lines. These steps should save you a few bucks too, since taking your lawn mower to a professional can be expensive.
Before putting your Husqvarna mower away for the winter months, remember to empty the mower of hydraulic oil at the end of every season.
Problem #4. Your lawn mower isn’t starting.
It’s no fun when your lawn mower won’t start up or has problems while you attempt to start it up. Don’t panic. Usually, following a few simple steps can nip this problem in the bud.
- Check that your lawn mower has sufficient fuel in its tank.
- Also, check the neutral control level.
- Make sure to double-check all the mower’s settings before starting the ignition or choking the engine.
Another culprit could be bad or old fuel in the mower’s carburetor float bowl. After some years, various ingredients in the lawn mower’s fuel can evaporate. The result? It’ll leave a stickier, thicker substance in its place.
As you might expect, this sticky fuel can completely block up the carburetor and, thus, stop the mower’s engine from starting. If you think you have a clogged carburetor, attempt to clean it with a good quality carburetor cleaner.
You might also want to check out the spark plugs of your lawn mower. If an electrode is damaged or burnt away; the porcelain insulator is damaged or cracked; or if there’s a heavy carbon buildup at the electrode, get the spark plug replaced.
To find out if the spark plug is defective or not, use a spark plug tester. When the engine is cranked up, you should see a significant spark from the spark plug tester’s terminals. If you don’t see any spark, this could be an indicator of a defective spark plug that needs to be replaced.
Problem #5. Your lawn mower isn’t moving forward or backward.
If your Husqvarna lawn mower isn’t moving forward or backward, the culprit could be old hydraulic fluid. The fluid could also be too low or even too hot.
That being said, air trapped in the lines of the hydraulic system or worn, broken, or loose drive belts could cause the mower not to move forward or back.
Check that the bypass control lever is in the “engaged” position. It should be both pushed in and pulled up. Oftentimes, the problem is that the lever isn’t in the right position, causing the mower to not move backward or forward.
If the axle key is missing in a Husqvarna lawn mower, or if the tensioner spring and pulley are broken, your mower won’t move back or forward. If you changed your mower’s tire recently, there’s a chance you could’ve missed a tiny key that fell out of the axle. It looks like a narrow, small bar. In order for your mower’s wheels to move, the axle key has to be installed.
Before doing any work on your mower, shut off the engine and take out the spark plug wire. Be very careful when you’re working around a hot transmission so that you don’t get burned.
If you’re still having problems with your lawn mower, find your local, authorized servicing dealer. They can evaluate and repair your mower for you.
Also, it’s worth noting that you should be wary of long periods of non-active hydrostatic drive transmission because this isn’t very good for the mower.
Why Won’t My Riding Mower Go Forward or Reverse?
If your riding mower won’t move forward or go into reverse, it could be one of many potential reasons for this.
- The mower doesn’t have the axle key in position. As mentioned earlier, the mower can’t work without an axle key.
- There could be a bad Husqvarna lawn mower tensioner pulley. Thesetensioner pulleys are, more often than not, crafted from hard plastics. At the center, there’s a bearing. It’s possible for the bearing to fail or the pulley can break. Always replace any bad pulleys with new ones. Be sure that the mower’s belt is inside the belt keepers and secured around the pulleys.
- Your lawn mower could also have old hydraulic oil or a low hydraulic fluid level. Some of the Husqvarna riding mower’s transmission systems are sealed and unserviceable. What this means for you is that you can’t change the hydraulic oil. To figure out whether or not you need to get your mower regularly serviced on its transmission, check your operator’s manual. If your lawn mower does have a transmission that’s serviceable, changing the hydraulic oil at consistent intervals that are recommended by Husqvarna should be completed. If you run your lawn mower with low or old hydraulic oil, it’ll cause the mower to seem weak while running or not move at all.
- The fluid could be too hot. However, this is a sign of more serious, extensive damage. If this is the case, consider taking your mower to a local Husqvarna dealership near you.
- The Husqvarna manual transmission bypass lever could be in the wrong position. If that’s the case, putting it in the right position can fix the issue.
- It’s possible that air has found its way into the Husqvarna’s hydraulic system. If this is the problem, you might notice your mower moving slowly. To fix this, as mentioned above, you’ll need to bleed the air out of the mower’s system.
- The Husqvarna mower’s belt could be broken, loose, or worn. If that’s the case, replace the affected parts.
- There could also be a missing or worn idler arm spring. The idler arm spring’s purpose is to create tension on the mower’s drive belt. If it’s broken, stretched, or missing, replace the spring. Be sure to keep the tensioner arm greased and lubricated, so it can move properly and won’t completely seize up.
If your mower’s engine shuts off or starts to splutter, check for the following items as well:
- A dirty carburetor
- A plugged or clogged fuel filter and fuel lines
- The mower’s battery and charging system
- A plugged or blocked air filter
Ruben has been doing online marketing for the last 4 years. Prior to that, he spent 15 years managing different brick-and-mortar businesses, in the home improvement and logistics industries. Overall, he has 20 years of business experience under his belt. Recently, he added SEO, affiliate marketing, and link building to his business skills.