Begin the system diagnosis by reviewing the Rear Axle Disassembled Views , Rear Drive Axle Description and Operation , and Transfer Case Description and Operation in Transfer Case - NVG900. Reviewing the description and operation information will help you determine the correct symptom diagnostic procedure when a malfunction exists. Reviewing the description and operation information will also help you determine if the condition described by the customer is normal operation. Refer to Symptoms - Rear Drive Axle procedure for diagnosing the system.