Strategy Based Diagnostics
Review the system in order to familiarize yourself with the system functions. Refer to
Rear Drive Axle Description and Operation and
Transfer Case Description and Operation for the NVG 760 transfer case. All diagnosis on a vehicle should follow a logical process.
Strategy based diagnostics is a uniform approach for repairing all systems. The diagnostics flow may always be used in order to resolve a system problem. The diagnostic flow is the place to start when repairs are necessary. For a detailed explanation, refer
to
Strategy Based Diagnosis.
Visual/Physical Inspection
| • | Inspect the easily accessible or visible system components for obvious damage or a condition which could cause the symptom. |
| • | Check for correct lubricant level and proper viscosity. |
| • | Verify the exact operating conditions under which the concerns exist. Note factors such as speed, road conditions, ambient temperature, and other specifics. |
| • | Compare the driving characteristics or sounds, if applicable, to a known good vehicle and make sure you are not trying to correct a normal condition. |
| | Caution: Do not exceed more than 5 seconds of parking brake application. RDM damage may result.
|
| • | Rear axle activation and operation may be checked by positioning the four wheels off the ground, starting the vehicle, and selecting the drive position. A properly operating rear axle and transfer case will rotate all four
wheels at equal RPM. Fully apply the parking brake, the rear will stop turning. Apply the throttle while watching the rear wheels. They will rotate slightly as the driveline winds-up. This indicates the all wheel drive (AWD) is functioning. Rear wheel must be
less than 5 kph when the parking brake applies. The CCM has a strategy that it will disable torque output when the rear wheel speed is 5 kph or more |
| • | Factors that may contribute to an inoperative rear axle include: |
| - | A mini spare or different size tires |
| - | A fluid over-temperature condition |
| - | A defective rear axle assembly |
| - | An inoperative transfer case assembly |
Intermittent
Test the vehicle under the same conditions that the customer reported in order to verify the system is operating properly.
Noise Acceptability
A gear driven unit will produce a certain amount of noise. Some noise is acceptable and audible at certain speeds, or under various driving conditions, such as a newly-paved blacktop road. Slight noise is not detrimental to the operation of the axle and
is considered normal.
Symptom List
Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom:
