Initial Inspection and Diagnostic Overview

Inspection and Verification
To guarantee an accurate diagnosis:
^ get an accurate description of the condition.
^ identify when the condition occurs; when hot or cold, during shifting, driving at a particular speed or in a particular gear.
^ have the customer demonstrate the concern, if possible.
^ refer to the Symptom Chart for additional source information and suggested test procedures. Symptom Related Diagnostic Procedures
^ carry out the following Noise Evaluation procedures, as necessary.

Noise Evaluation

NOTE: Carry out this evaluation with the transmission cold and at normal operating temperature to listen for any change in noise as the transmission warms up.

1. Start the engine.
The clutch master cylinder transmits fluid pressure to the clutch slave cylinder, which in turn moves the clutch release hub and bearing. The clutch hydraulic system uses brake fluid and has a separate reservoir. The clutch is a single plate, dry-friction disc with a diaphragm-style spring pressure plate. The clutch disc has frictional material where it contacts the flywheel and the clutch pressure plate. the clutch pressure plate applies pressure to the clutch disc, holding it tightly against the surface of the flywheel.
In the engaged position, the clutch pressure plate diaphragm spring holds the clutch pressure plate against the clutch disc, so that the engine torque is transmitted to the input shaft. When the clutch is depressed, movement is transmitted through the clutch hydraulic system, which actuates the clutch release hub and bearing. The clutch release hub and bearing pushes on the spring center towards the flywheel. The diaphragm spring pivots at the fulcrum, relieving the load on the clutch pressure plate. Steel spring straps riveted in the clutch pressure plate cover pull the clutch pressure plate from the clutch disc, disengaging the engine torque from the transmission.
2. Evaluate the noise in NEUTRAL while the vehicle is parked.
3. Listen for any change in noise while depressing and releasing the clutch pedal.
4. Listen for any change in noise while changing the engine rpm.
5. Drive the vehicle and shift through all of the gear ranges, including REVERSE. Listen for any change in noise in a particular gear.
6. Drive the vehicle in the gear in which the noise is most noticeable. Depress the clutch pedal and leave the gear engaged. Listen for any change in noise. The vibration of the engine may be amplifying the noise.
7. Drive the vehicle under the same conditions identified in the previous step. Depress the clutch pedal and shift the transmission into NEUTRAL. Release the clutch pedal and allow the vehicle to coast. Evaluate the noise as the rear axle assembly turns the mainshaft.

Additional Testing for 4x4 Trucks
^ Check for any noise change when shifting the transfer case between 2H, 4H, 4L or into NEUTRAL.
^ With the vehicle at a complete stop and the transfer case in NEUTRAL, shift through all the gears and evaluate the noise at different engine rpm. Check for any noises in NEUTRAL at different engine rpm.