The John Deere LA135 is a popular lawn tractor among homeowners for its power and convenience, but it’s not without its quirks. Many owners eventually run into recurring issues that can turn routine mowing into a headache. Understanding the most common problems, their causes, and practical solutions can help you keep your LA135 running smoothly season after season.
Engine Starting Troubles
One of the most frequent complaints about the John Deere LA135 is trouble starting the engine. Typically, this shows up as a slow crank, a click with no turnover, or no response at all when turning the key. Old or weak batteries are a leading culprit, especially after winter storage when batteries may have discharged. Corroded battery terminals or loose connections can also block current flow. Inspect these first, cleaning terminals and tightening connections as needed.
If the battery and connections check out, look at the starter solenoid and ignition switch. These components can wear out with age and use, producing intermittent or failed starts. Replacing a solenoid is straightforward and can restore reliable starting. Also, consider the condition of the spark plug and fuel filter - both can cause no-start conditions if fouled or clogged.
Transmission and Hydrostatic Drive Problems
The LA135 uses a Tuff Torq K46 hydrostatic transmission, which is known to show problems as the tractor ages, especially with heavy use or inadequate maintenance. Owners often report a loss of forward or reverse power, sluggish movement, or complete failure to move when the pedal is engaged. Over time, the internal components of the transmission can wear, and the hydraulic fluid may degrade or leak.
Unfortunately, this transmission is sealed and not intended for user-serviceable fluid changes, but some owners tackle the job anyway by removing the unit and refilling with fresh 10W-30 synthetic oil. This can sometimes extend the lifespan, but once symptoms appear, the damage may be done. Avoid hauling heavy loads or mowing steep slopes, as these put extra strain on the transmission. Regularly check for leaks beneath the tractor and keep the cooling fan and fins clear of debris to prevent overheating.
Cut Quality and Deck Issues
Uneven cuts, scalping, or streaks are common deck-related complaints with the LA135. The 42-inch Edge mower deck can develop problems with blade alignment, spindle wear, or deck leveling. Often, owners find that the cut quality declines as the deck ages or after hitting a hidden object in the yard. Decks that are not properly leveled from side to side or front to back can leave uncut strips or cause the tractor to scalp the lawn in spots.
Check the mower blades for dullness, nicks, or warping. Sharpen or replace blades as needed. Deck leveling is essential and can be adjusted using the lift links and front draft rod. Also, inspect the deck belt for wear and proper tension - a slipping belt can cause blades to spin inconsistently, leading to poor results.
Electrical System Faults
Electrical issues surface regularly in LA135 tractors, especially as wires and connectors age. Symptoms include headlights not working, intermittent starting, or accessories failing unexpectedly. In many cases, the cause is corrosion at the wiring harness connections or moisture ingress at switches and relays.
Begin diagnosis with a visual inspection of wires, connectors, and fuses. Clean and tighten any corroded or loose terminals. The seat safety switch is notorious for failing or getting stuck, which can prevent the engine from running if it thinks the seat is unoccupied. Bypassing the switch temporarily can help narrow down the cause, but always replace faulty safety devices to avoid injury.
Steering and Front Axle Wear
Owners of the LA135 sometimes report excessive steering play, difficulty turning, or clunking noises from the front axle. Over time, the steering gear, bushings, and tie rods can wear out, especially if the tractor sees a lot of use or is operated over rough ground. A loose or wobbly front wheel is a telltale sign.
Inspect the steering linkage, drag link connections, and the pivot points on the front axle. Replacing worn bushings or tie rod ends is a straightforward repair and can restore tight, predictable steering. Applying fresh grease to all fittings will also extend the life of the steering components.
Fuel System Snags
If your LA135 sputters, surges, or stalls, a fuel system issue could be at the root. Common sources include a plugged fuel filter, deteriorated fuel lines, or a clogged carburetor. Ethanol-blended gasoline, which absorbs moisture, can speed up degradation of rubber lines and promote varnish buildup in the carburetor jets.
Replace fuel filters at least annually, and inspect lines for cracks or softness. For persistent running issues, remove and clean the carburetor, paying special attention to the main jet and float bowl. Running ethanol-free fuel or using a stabilizer can help prevent future problems.
PTO and Blade Engagement Problems
Some LA135 owners find the blades won’t engage or disengage properly. A faulty PTO (power take-off) switch, stretched PTO cable, or worn belt can all be to blame. The manual PTO lever should operate smoothly, and if it doesn’t, inspect the cable routing for kinks or the presence of excessive slack.
If the blades still refuse to spin, check the electric PTO clutch if equipped, or the idler pulleys and tensioner springs on the deck. Replacing a worn clutch or tightening a loose belt often solves engagement problems and gets the mower deck working again.
Frequently asked questions
What kind of oil does the John Deere LA135 use?
The LA135's engine takes SAE 10W-30 oil; use a high-quality detergent oil suitable for gasoline engines. The hydrostatic transmission is sealed, but some owners use 10W-30 synthetic for refills if servicing.
How do I level the mower deck on a John Deere LA135?
Park the tractor on a flat surface, lower the deck, and use a ruler to measure blade height at each side. Adjust the lift links and front draft rod until both sides are within 1/8 inch of each other.
Is the transmission on the LA135 serviceable?
Officially, the K46 transmission is sealed and not designed for fluid changes. Some owners remove and service the unit to replace fluid, but this is not a manufacturer-supported procedure.
Why does my LA135 lose power going uphill?
Loss of power on slopes often points to a worn hydrostatic transmission, especially if the tractor struggles more as it warms up. Heavy loads or old hydraulic fluid can make the issue worse.