Spicer Tandem Drive Axles Pro-40 Single Reduction and Single Reduction with Differential Lock - Manual (Page 8)

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Inspection
Inspection
Inspection
Failure Analysis
Failure analysis is the process of determining the original cause
of a component failure in order to keep 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, it is
not enough to settle on the broken tooth as the cause of the carrier
failure. Other parts of the carrier must be examined. For a thorough
understanding of the failure and possible insight into related
problems, the technician needs to observe the overall condition
of the vehicle.
No one benefits when a failed component goes on the junk
pile with the cause unknown. Nothing is more disturbing to a
customer than a repeat failure. Systematically analyzing a failure
to prevent a repeat occurrence assures quality service by
avoiding unnecessary downtime and further expense to the
customer.
The true cause of a failure can be better determined by knowing
what to look for, determining how a piece of the equipment
was running and learning about previous problems. In the case
of a rebuilt rear axle, mismatched gears may have been installed.
The more successful shops prevent repeat equipment failures
by developing good failure analysis practices. Knowing how to
diagnose the cause of a premature failure is one of the
prerequisites of a good heavy-equipment technician.
How to Diagnose a Failure
The following five steps are an effective approach to good failure
diagnostics.
1. Document the problem.
2. Make a preliminary investigation.
3. Prepare the parts for inspection.
4. Find the cause of the failure.
5. Correct the cause of the problem.
Document the Problem
Here are some guidelines for starting to learn about a failure,
including questions to ask:
1. Talk to the operator of the truck.
2. Look at the service records.
3. Find out when the truck was last serviced.
4. Ask: In what type of service is the truck being used?
5. Ask: Has this particular failure occurred before?
6. Ask: How was the truck working prior to the failure?
You need to be a good listener. Sometimes, insignificant or
unrelated symptoms can point to the cause of the failure:
7. Ask: Was the vehicle operating at normal
temperatures?
8. Ask: Were the gauges showing normal ranges of
operation?
9. Ask: Was there any unusual noise or vibration?
After listening, review the previous repair and maintenance
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. Verify the chassis Vehicle
Identification Number (VIN) number from the vehicle identification
plate, as well as the mileage and hours on the vehicle.
Make a Preliminary Investigation
These steps consist of external inspections and observations
that will be valuable when combined with the results of the
parts examination.
1. Look for leaks, cracks or other damage that can
point to the cause of the failure.
2. Make note of obvious leaks around plugs and seals.
A missing fill or drain plug would be an obvious
cause for concern.
3. Look for cracks in the carrier housing (harder to see,
but sometimes visible).
4. Does the general mechanical condition of the vehicle
indicate proper maintenance or are there signs of
neglect?
5. Are the tires in good condition and do the sizes
match?
6. If equipped with a torque-limiting device, is it working
properly?
During the preliminary investigation, write down anything out
of the ordinary for later reference. Items that appear insignificant
now may take on more importance when the subassemblies
are torn down.