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.
Fig 1: View Of Thrust (Pump To Drum) Washer
Courtesy of GENERAL MOTORS CORP.
Remove the thrust (pump to drum) washer (601).
Fig 2: View Of Oil Pump Cover & Oil Pump Body
Courtesy of GENERAL MOTORS CORP.
Remove the pump cover bolts (233).
Remove the pump cover (215) from the pump body (200).