Auto Adjuster (Drum Brake)
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 1990 Pontiac Bonneville, 1990 Oldsmobile Ninety-Eight, 1990 Oldsmobile Eighty-Eight, 1990 Cadillac Fleetwood, and 1990 Cadillac DeVille. However, it is still accessible from the selected car via links, so may be relevant.
Drum brake adjustment is automatic whenever brakes are applied. It is normal for the leading shoe to wear faster than the trailing shoe.