GMC 1995 Safari Owner's Manual page 237

Brake Wear
Your Vehicle has front disc brakes and rear drum brakes.
Disc brake pads have built-in wear indicators that make a high-pitched
warning sound when the brake pads are worn and new pads are needed. The
sound may come and go or be heard all the time your vehicle is moving
(except when you are pushing on the brake pedal firmly).
NOTICE:
Continuing to drive with worn-out brake pads could result in
costly brake repair.
Some driving conditions or climates may cause a brake squeal when the
brakes are first applied or lightly applied. This does not mean something is
wrong with your brakes.
Your rear drum brakes don't have wear indicators, but if you ever hear a
rear brake rubbing noise, have the rear brake linings inspected. Also, the
rear brake drums should be removed and inspected each time the tires are
removed for rotation or changing. When you have the front brakes replaced,
have the rear brakes inspected, too.
Brake linings should always be replaced as complete axle sets.
Brake Pedal Travel
See your dealer if the brake pedal does not return to normal height, or if
there is a rapid increase in pedal travel. This could be a sign of brake
trouble.
Brake Adjustment
Every time you make a brake stop, your disc brakes adjust for wear.
If your brake pedal goes down farther than normal, your rear drum brakes
may need adjustment. Adjust them by backing up and firmly applying the
brakes a few times.
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