1. Axle Abnormal Noise

1.1 Constant Humming Noise Increasing with Speed

• Improper backlash or contact pattern of main reducer gears
• Wear, pitting or broken teeth of wheel hub reduction gears
• Worn or loose wheel hub bearings
• Excessive clearance of differential gears

• If noise remains during coasting: check wheel bearings and wheel reducers
• If noise reduces in neutral: inspect main reducer and differential
• If noise worsens in turns: focus on differential and side gears

• Adjust gear backlash and contact pattern; replace worn gears
• Replace faulty bearings and adjust preload to standard torque
• Replace damaged differential gears and thrust washers

1.2 Metallic Knocking & Impact Noise (During Acceleration or Shifting)

• Excessive gear clearance in main reducer or differential
• Worn axle shaft splines or loose hub matching
• Loose flange nuts or drive shaft connections
• Loose U-bolts causing axle housing displacement

• Readjust gear clearances and retighten all fasteners
• Replace axle shafts or hubs if splines are excessively worn
• Retorque U-bolts and axle mounting brackets

1.3 Sharp Friction Noise

• Abnormal friction between brake pads/shoes and drums/discs
• Oil leakage contaminating braking surfaces
• Axle housing deformation or bearing seizure

• Replace brake components and resurface brake drums
• Replace axle shaft or hub oil seals to stop leakage
• Straighten or replace deformed axle housing

2. Axle Oil Leakage

2.1 Oil Leakage at Wheel Hub or Axle Shaft

• Aging, wear or damaged oil seals
• Scratched or corroded shaft journals
• Loose wheel bearings causing excessive runout
• Overfilled gear oil increasing internal pressure

• Replace genuine-spec oil seals
• Repair minor shaft wear; replace severely damaged parts
• Adjust bearing preload to control runout
• Fill gear oil to the correct level only

2.2 Leakage at Main Reducer Housing or Joint Surfaces

• Damaged or deteriorated gaskets
• Loose housing bolts or insufficient torque
• Deformed or uneven mating surfaces

• Clean surfaces, replace gaskets and apply high-temperature sealant
• Retighten bolts diagonally to standard torque
• Repair or replace deformed axle housing

2.3 Oil Blowout Due to Clogged Breather Valve

• Dust, mud or water blocking the breather
• Internal pressure buildup breaking oil seals

• Clean and unclog the breather regularly
• Replace damaged seals after pressure relief

3. Axle Overheating

3.1 Excessive Heat at Wheel Hubs

• Excessive wheel bearing preload
• Brake drag or non-returning calipers
• Tight oil seals causing dry friction
• Poor lubrication in wheel reducers

• Readjust bearing preload to factory specifications
• Repair brake calipers, return springs and wheel cylinders
• Replenish or replace special lubricant for wheel reducers

3.2 Overheating at Main Reducer

• Insufficient, degraded or mismatched gear oil
• Insufficient gear backlash increasing friction
• Damaged or seized differential bearings

• Replace qualified gear oil (80W-90 / 85W-140)
• Readjust gear backlash
• Replace worn or damaged bearings

4. Vehicle Pulling, Steering Wheel Vibration & Poor Stability

4.1 Vehicle Pulling to One Side

• Uneven wheel bearing preload left and right
• Uneven brake clearance or one-sided brake drag
• Incorrect toe-in, caster or camber angles
• Uneven leaf spring tension or loose U-bolts
• Bent axle housing

• Balance bearing preload on both sides
• Adjust brakes for balanced braking force
• Perform four-wheel alignment
• Inspect and replace deformed axle housing

4.2 Steering Wheel Vibration at High Speed

• Loose or worn wheel hubs
• Deformed rims or poor dynamic balance
• Bent axle shafts or unbalanced drive shafts
• Poor meshing of main reducer gears

• Retighten or replace wheel hub bearings
• True rims and rebalance wheels
• Check axle shaft runout and replace if necessary

5. Wheel Hub Bearing Failure & Looseness

• Abnormal noise and vehicle swaying
• High hub temperature; obvious tire wobble
• Possible seizure in severe cases

• Lack of lubrication or water contamination
• Overloading and frequent heavy braking
• Improper installation torque
• Dust ingress due to seal failure

• Replace inner and outer bearings as a set
• Clean axle hubs, dry and apply high-temperature grease
• Torque bearings strictly per standard procedure
• Replace oil seals simultaneously to prevent recontamination

6. Differential Malfunctions

• Noise or resistance during turns
• One-wheel spin with poor traction
• Differential lock failure to engage or disengage

• Worn or seized differential spider/side gears
• Faulty differential lock cylinders or linkage
• Insufficient gear oil and poor lubrication

• Inspect gears and replace differential assembly if needed
• Repair differential lock actuators and air lines
• Maintain proper gear oil level and quality

7. Early Gear Wear, Pitting & Tooth Breakage

• Low-quality gear oil or extended oil change intervals
• Overloading, aggressive driving and high-torque starts
• Incorrect gear meshing adjustment
• Water entering axle housing causing oil emulsification

• Use factory-recommended gear oil and change regularly
• Avoid overloading and harsh operation
• Replace gear sets as a pair if severely worn

8. Preventive Maintenance for Axle Systems

• Check oil level, seals and bolt torque every 10,000 km
• Change gear oil every 30,000–60,000 km based on working conditions
• Follow standard installation procedures for bearings, seals and gears
• Avoid deep water crossing to prevent water intrusion
• Keep breather valves clean and unobstructed
• Strictly control vehicle loading within rated capacity