AXSM0055P Service Manual

This symbol is used throughout this manual to call attention to procedures where carelessness or failure to follow specific instructions may result in serious injury and / or damage to the component.

Ignore the instructions, choice of tools, materials and recommended parts mentioned in this publication may jeopardize the safety of the service technician or vehicle operator.

WARNING: Failure to follow the indicated procedures creates a high risk of injury to the maintenance technician.

CAREFUL: Failure to follow the indicated procedures may cause damage to the component.

IMPORTANT: Highly recommended procedures for proper repair of this unit.

OBSERVATION: Additional service information does not cover service procedures.

TIP: Helpful removal and installation procedures to aid in the maintenance of this equipment.

DEM: Refer to vehicle OEM specifications

Failure analysis is the process of determining the original cause of a component failure to prevent it from happening again. Too often, when a failed component is replaced without determining its cause, there will be a recurring failure.

If a carrier housing is opened, revealing a ring gear with a broken tooth, this is sufficient to establish the broken tooth as the cause of the carrier failure. Other parts of the carrier should be examined.

For a complete understanding of the failure and possible insight into related problems, the technician needs to observe the overall condition of the vehicle.

There is no benefit when a failed component goes to the scrap heap with the cause unknown. It's no more annoying to a customer than a repeat failure.

Systematically analyzing a failure to prevent the occurrence from happening again guarantees quality service, avoiding unnecessary downtime and more expenses for the customer.

The true cause of a failure can be determined best if you know what to look for, determine which piece of equipment was malfunctioning, and learn from previous problems. In the case of a rebuilt rear axle, mismatched gears may have been installed.

The most successful shops prevent equipment failure from recurring by developing good failure analysis practices. Knowing how to diagnose the cause of premature failure is one of the prerequisites of being a good heavy equipment technician.

The following five steps are an effective approach to good fault diagnosis.

Documents a problem.

Do a preliminary investigation.

Prepare parts for inspection.

Locate the cause of the failure.

Correct the cause of the problem.

Here are some guidelines for getting started with a failure, including questions to ask:

Talk to the truck operator.

Analyze the service logs.

Find out when the truck was last serviced.

Ask: What type of service is the truck being used for?

Ask: Has this specific failure occurred before?

Ask: How was the truck operating before the failure?

You need to be a good listener. Sometimes, insignificant or seemingly unrelated symptoms can indicate the cause of the failure:

Ask: Was the vehicle operating at normal temperatures?

Ask: Were the gauges showing normal operating variations?

Ask: Was there any abnormal noise or vibration?

After listening, review previous maintenance and repair records. If there is more than one driver, talk to all of them and compare their observations for consistency with the service and maintenance records.

Check the chassis number VIN (Vehicle Identification Number) from the vehicle's nameplate, as well as the vehicle's mileage and operating hours.

These steps consist of external inspections and observations that will be valuable when combined with the results of the parts examination.

Look for leaks, cracks or other damage that may indicate the cause of the failure.

Make notes of obvious leaks around plugs and seals. A missing drain or fill plug should be an obvious cause for concern.

Look for cracks in the bracket housing (hard to see, but sometimes visible).

Does the overall mechanical condition of the vehicle indicate proper maintenance or are there signs of neglect?

Are the tires in good condition and the correct size?

If equipped with a torque limiting device, is it functioning properly?

During the preliminary investigation, note anything that appears abnormal for later reference. Items that seem insignificant can now take on more importance when subassemblies are disassembled.

After preliminary investigation, locate the fault and prepare the part for examination. In analyzing the fault of the bracket, it may be necessary to disassemble it.

When disassembling parts and subassemblies, do not clean the parts immediately, as cleaning may destroy some evidence.

When breaking the drive shaft, do so in the recommended manner. Minimize any additional damage to the equipment.

Ask more questions when examining the inside of the mount. Does the lubricant meet the manufacturer's specifications for quality, quantity, and viscosity? Once you locate the defective part, analyze the data carefully.

Here begins the real challenge of determining the exact cause of the defect. Remember, there is no benefit in replacing a defective part without determining the cause of the defect.

For example, after examining a faulty part and discovering that the failure was caused by a lack of lubricant, you must determine whether there was an external leak. Obviously, if there is an external leak, replacing the faulty gear will not correct the situation.

Another important consideration is determining the specific type of failure, which can be a valuable indicator of the cause of the failure. The following pages show different types of failures and their possible causes. Use them as a guide to determining the types of failures and correcting the problems.

Once the cause of the problem has been determined, refer to the appropriate maintenance manual to perform repairs.

Wash steel parts with polished or ground surfaces with solvent. There are many suitable commercial solvents available. Kerosene and diesel oil are acceptable.

WARNING: Gasoline is not an acceptable solvent because of its extreme flammability. It is not safe for a workshop environment.

Wash castings or other raw parts in solvent or clean in hot solution tanks using mild alkaline solutions.

Note: If a hot solution tank is used, make sure parts are fully heated before rinsing.

Rinse thoroughly to remove all traces of the cleaning solution.

Dry the parts immediately with clean cloths.

Parts with oil.

If parts are to be reused immediately: Lightly oil them. If parts are to be stored: Coat them with oil, wrap them in anti-corrosion paper, and store in a clean, dry place.

Inspection and repairs to the axle housing are limited to the following checks or repairs.

Visually inspect the shaft housing for cracks, splits and burrs on the machined surfaces.

Check the studs and bracket bolt holes for foreign material.

Replace damaged fasteners. Check for loose screws or cross-threaded holes.

CAUTION: Any damage that affects the alignment or structural integrity of the housing requires replacement of the housing. Do not repair by bending or straightening. This process can affect the material properties and cause it to fail completely under load.

Check all seals and gaskets.

Note: Replace conventional gaskets with silicone rubber gasket compound (included in many repair kits). The compound provides a more effective seal against lubrication ingress and is easier to remove from mating surfaces when replacing parts.

Inspect all steel parts for:

Visible notches, steps or grooves created by wear.

Corrosion or cracking along gear contact lines.

Friction, deformation or discoloration. These are signs of excessive heating in the shaft and are usually related to low lubrication levels or incorrect lubrication practices.

Additionally, inspect the following items for damage:

Differential gear.

Bearings for loose fittings on the transmission pinion and differential bearings.

All fasteners for rounded heads, warping, cracks or damaged threads.

Inspect the machined surfaces of castings or malleable parts. They should be free of cracks, splits, scoring and wear.

Look for enlargement of drilled holes, wear on machined surfaces for bearing fits, and cracks or burrs on mating surfaces.

Before reusing a primary gear set, inspect the teeth for signs of excessive wear. Check the tooth contact pattern for evidence of improper fit.