Diagnostic Aids

Inspect the flywheel ring gear for damage or unusual wear.
Shim the starter if applicable.
In order to add pinion to ring gear clearance a full size shim must be used. Do not shim only 1 starter mounting bolt. There are 3 shims available in different shapes (for clearance). All are 1 mm (0.039 in) thick.

Fig 1: Starter Motor Noise Diagnosis Chart

Courtesy of GENERAL MOTORS CORP.