Spicer Drive Axles Failure Analysis Service Manual - Manual (Page 20)

Failure Analysis
19
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.
• Look for leaks, cracks or other damage that can point to the cause of the failure.
• Make note of obvious leaks around plugs and seals. A missing fill or drain plug would be an obvious cause for concern.
• Look for cracks in the carrier housing (harder to see, but sometimes visible).
• Does the general mechanical condition of the vehicle indicate proper maintenance or are there signs of neglect?
• Are the tires in good condition and do the sizes match?
• 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.
Prepare the Parts for Inspection
After the preliminary investigation, locate the failure and prepare the part for examination. In carrier failure analysis, it may be nec-
essary to disassemble the unit.
• When disassembling subassemblies and parts, do not clean the parts immediately since cleaning may destroy some of
the evidence.
• When tearing down the rear axle, do it in the recommended manner. Minimize any further damage to the unit.
• Ask more questions when examining the interior of the carrier. Does the lubricant meet the manufacturer specifications
regarding quality, quantity, and viscosity? As soon as you have located the failed part, take time to analyze the data.
Find the Cause of the Failure
Here begins the real challenge to determine the exact cause of the failure. Keep in mind that there is no benefit to replacing a failed
part without determining the cause of the failure. For example, after examining a failed part and finding that the failure is caused
by a lack of lubrication, you must determine if there was an external leak. Obviously, if there is an external leak, just replacing the
failed gear is not going to correct the situation.
Another important consideration is to determine the specific type of failure which can be a valuable indicator for the cause of fail-
ure. The following pages show different types of failures and possible causes. Use this as a guide in determining types of failures
and in correcting problems.
Correct the Cause of the Problem
Once the cause of the problem has been determined, refer to the appropriate Service Manual to perform the repairs.