GM Service Manual Online
For 1990-2009 cars only

Important: 

   â€¢ Do not reinstall the original cast iron production shims, if removed. Once the cast iron shims are removed from the axle housing, they must be replaced with service shims and spacers.
   â€¢ If service shims were previously installed, the shims can be reused.

Inspect the shims for cracks and chips. Replace the damaged shims.