WARNING: This page is about a different car, the 2003 Chevrolet Monte Carlo and 2003 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Crankshaft Balancer Sealing Area
Courtesy of GENERAL MOTORS CORP.
Inspect the crankshaft balancer sealing area for grooves (1).
Inspect the crankshaft balancer belt ribs for dents or damage.