GM 6.5L V8 – Electrical Systems – Related Diagnosis/Service Procedures – Cranking Motor Noise Diagnosis

1. Listen to the cranking system during cranking (before the engine starts):
• If a high-pitched whining noise exists, decrease the distance between the pinion and flexplate gear teeth by subtracting shims.
• If a high-pitched whining noise does not exist, go to step 2.

2. Listen to the cranking system during cranking (after the engine starts):
• If a high-pitched whining noise exists, increase the distance between the pinion and flexplate gear teeth by adding shims.
Note: If the high-pitched whining noise is rhythmic, check the runout of the flexplate gear teeth.

• If a loud “whoop” sound exists (and changes in pitch as engine speed changes), replace the cranking
motor clutch.
• If a rumbling, growling or knocking noise exists, inspect the cranking motor armature for imbalance or a bent shaft.
• If none of the above noises exist, go to step 3.

3. Listen to the cranking system after cranking (as the ignition switch moves from the CRANK to RUN
position):
• If a rumbling, growling or knocking noise exists, inspect the cranking motor armature for imbalance or a bent shaft.

 

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