WARNING: This page is about a different car, the 2008 Isuzu Ascender, 2008 GMC Envoy, and 2008 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.
Ratcheting Noise
Checks
Causes
Parking Brake Pawl (50-81)
The parking pawl return spring is weak, damaged, or misassembled