ATVs travel through sand, mudflats and gravel roads for a long time. Sand, dust and water vapor can easily enter the gearbox. Coupled with frequent slipping and impact loads during driving, gears will produce various specific faults, and the external performance and formation causes of each fault are different.

Abrasive tooth surface wear is the most frequent fault of ATV gears. Fine sand enters the gear meshing area through sealing gaps and acts as abrasive to continuously scrape the tooth surface during operation. Over time, the original smooth lines of the tooth surface are worn flat. The vehicle will produce continuous fine noise during acceleration, and the climbing power will decrease significantly. Most of such faults are caused by aging oil seals and damaged box cover gaskets. Failure to clean the sediment outside the box after off-roading will accelerate the wear process.

Tooth surface pitting and spalling mostly occur on ATVs that often run with full loads. Repeated alternating loads brought by terrain fluctuations make the tooth surface bear cyclic extrusion for a long time. The surface metal gradually appears dotted pits, and small pieces of metal fall off to form peeling gaps in the later stage. A clear impact noise will be heard when releasing the accelerator and then speeding up during driving, and intermittent transmission stuttering will occur in severe cases, mostly caused by insufficient toughness of gear materials or long-term failure to replace special lubricating oil.

Gear tooth breakage is a highly dangerous fault. When the vehicle rushes up slopes at high speed or the wheels are stuck on stones, an excessive impact load is generated in an instant, and the stress concentrates on the weak position of the tooth root, directly causing single or multiple tooth breakage. A violent metal impact sound will be heard the moment the fault occurs, and the vehicle will directly lose forward power. If driving forcibly, the broken metal fragments will damage surrounding accessories such as the box and bearings, greatly increasing maintenance costs.

Abnormal deviation of gear meshing clearance is also very common. Long-term bump vibration will cause bearing clearance, driving the gear axis to misalign, making one side of meshing tight and the other loose. The noise is weak during constant-speed driving, but the abnormal noise will be sharply amplified when turning or driving on bumpy roads, accompanied by slight body vibration, mostly caused by long-term neglect of bearing and adjusting gasket inspection.

Gear rust faults are common in ATVs that are parked for a long time or used by the sea. Salt-containing water vapor from tidal flats seeps into the box. After the protective performance of lubricating oil declines, rust spots form on the tooth surface. The rust layer will aggravate meshing friction. The noise is harsh when starting the cold vehicle, and the abnormal noise is slightly reduced after short-distance driving and temperature rise. Failure to deal with it for a long time will gradually develop into deep corrosion damage.

In daily use, cleaning sediment after each off-road trip, regularly replacing gear oil suitable for off-road working conditions, and timely replacing aging seals can effectively reduce the probability of the above various gear faults.