6 Common John Deere GT235 Problems & Fixes

Owning a john deere gt235 can be a lot of fun. It’s an excellent lawnmower for farmers and homeowners alike. However, like any other machinery, it can experience problems from time to time.

The most common John Deere GT235 problems are general poor engine performance, issues with the hydrostatic transmission, the mower cutting out and then not turning over, and some trouble with the electrics.

In this article, we will discuss some of the most common john deere gt235 problems that you may have to deal with, ways to diagnose them, and tips for repairing them.

Poor Engine Performance

One of the most common john deere gt235 problems is poor engine performance. Several things can cause this, but the most common cause is dirty fuel. Make sure you use clean fuel in your mower and that the fuel filters are clean.

The generally poor performance of your lawnmower is also the main symptom of engine damage. Remove the valve covers and take a look; I’ve seen the push rods completely bent out of shape and removed from the exhaust valve. You’ll need to either straighten the rod or completely replace it and put it back in its correct position.

One piece of information to note, a lot of engine problems are down to using cheap ethanol fuel. If you leave it sitting in the tank too long, the cheap fuel breaks down, and this causes the valves to stick due to a lack of lubrication.

It’s essential to use quality fuel in your lawnmower, and not only that, but if you leave old gas for too long between runs, you’ll have to drain it and get some fresh fuel in there. As I mentioned, dirty fuel is the number one culprit for engine problems.

Hydrostatic Transmission Issues

The John Deere GT235 uses a hydrostatic transmission. This transmission type is filled with oil and pressurized by the engine’s pumping action. The pressurized oil is what powers the wheels.

Over time, the seals in the transmission can break down, causing oil to leak out. When this happens, the transmission will not have enough oil and eventually fail.

If you notice oil leaking from your John Deere GT235, it is important to troubleshoot why it’s happening and repair it immediately.

The hydrostatic transmission can also produce a loud, whining sound when you see the brake, even if the mower isn’t being used, or it will only edge forward and not reverse at all; if you’re getting either of these symptoms, following these steps to diagnose the problem,

  • Ensure the transmission fluid is topped up to the correct level.
  • Double check the transmission is securely bolted to its bracket; they can come loose.
  • Test the ease with which you can push the mower, and do the same with the transmission release lever; what you’re looking for here is to see if it’s resisting, which will tell you where the problem lies.
  • Bleed the transmission; check your manual for details on how to do this.
  • Let the engine sit idly with the throttle closed and then open to see how the engine revs. Your lawnmower will move very slowly if the carburetor isn’t calibrated.
  • Now, with the engine off, attempt to spin the transmission drive belt; again, you’re looking for anything stopping this from moving freely.

If you still need to get to the bottom of the transmission issue, now may be the time to take it to the local repair shop.

John Deere GT235 Won’t Turn Over

If your John Deere GT235 doesn’t turn over, there could be several reasons.

One of the most common reasons why a john deere gt235 won’t turn over is because the battery is dead. Make sure the battery is fully charged and that the connections are clean and tight.

Another reason why your john deere gt235 won’t turn over could be because the starter solenoid is defective. This part can be found on the side of the engine and is easily replaced.

If the battery is in full working order, and the starter solenoid looks fine, you may be dealing with an electrical problem. Firstly, you’ll need to check all the fuses, ensuring none are blown and replacing any that have.

Make sure that all the connections are tight, with no debris or dirt on them. While you’re there, check every other electrical connection.

Electrical Problems

Talking of electrical problems, there’s more!

If you’re having problems turning the mower over or power issues and you’ve ruled out any battery or solenoid problems, it’s now time to turn your attention to the starter module and switch.

These have been known to fail on the GT235 and could need replacing.

You may also have a short circuit, inspect the wiring and replace anything that looks as if it has the potential to be faulty.

As a general rule, keep terminals clean, replace any old wiring and replace the battery regularly. I’d recommend getting hold of a gravity tester; they’re cheap and don’t just indicate the charge of the battery, but the health of each cell!

3-Point Hitch Lowering Problems

The 3-point hitch is a vital part of the john deere gt235, and its lowering function supports a range of attachments.

If you’re having problems with the hitch lowering too slowly or not at all, check for any blockages in the hydraulic lines or look for any leaks. Also, check that the control valve is operating correctly.

Another john deere gt235 problem that can cause the 3-point hitch to lower slowly is if the return spring is damaged or missing altogether. This spring helps to keep the platform up when it’s not in use, so it must be in good working order!

What usually causes a problem with your 3-point hitch is broken cables or belts, poor connections that have come loose, debris, or poor hydraulic fluid circulation.

Replacing the hydraulic pump would be ideal, but before you go to those measures, replace any poor wiring, ensuring connections are tight between the lift cover switch and electric wire harness.

Mower Deck Struggle to Engage

Finally, if you’re john deere gt235 is having trouble engaging the mower deck, the blades aren’t engaging, or it’s leaking fluid, the PTO clutch likely is to blame. This part can fail for several reasons, from wear and tear to lack of lubrication.

The first thing you need to do is make sure that there’s no debris or dirt around the PTO clutch, as this can cause it to slip.

Next, check for any wear and tear on the belts and replace them if necessary. If the PTO clutch is worn out, it will need replacing.

If the PTO clutch looks to be okay, check for any defective safety switches and worn-out pulleys, these can come loose and causes havoc in your mower.

Lastly, you can try replacing the anti-scalp bearings, the tensioners, and of course, the blades. Give the mower deck a thorough clean, and make sure the safety switches are in good working order.

If you need a hand getting to the mower deck, the video below will help:

Frequently Asked Questions:

What engine is in a John Deere GT235?

The John Deere GT235 mower has an 18hp, 2-cylinder engine. The engine manufacturer differs between Kawasaki and Briggs & Stratton.

What oil filter does a John Deere GT235 take?

The AM107423 oil filter is used on a John Deere GT235.

What size battery does a John Deere GT235 take?

The John Deere GT235 takes a 12V 35AH battery.


There you have it, 6 of the most common john deere gt235 problems and how to fix them. The John Deere GT235 is in the main, a solid lawnmower; it’s susceptible to a few issues, but hey, what isn’t these days?

It comes at a great price for the quality, and it’s a John Deere, so you know you’re getting a good product, even if it isn’t what it used to be.

As with all lawnmowers, give it some regular TLC, and it will serve you well for years to come!