GMC 2006 Sierra - Manual (Page 462)

Brake Wear
Your vehicle has front disc brakes and may have rear
drum brakes or rear disc 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.
{ CAUTION:
The brake wear warning sound means that soon
your brakes will not work well. That could lead
to an accident. When you hear the brake wear
warning sound, have your vehicle serviced.
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.
Properly torqued wheel nuts are necessary to help
prevent brake pulsation. When tires are rotated, inspect
brake pads for wear and evenly tighten wheel nuts in
the proper sequence to GM torque specifications.
If you have rear drum brakes, they do not have wear
indicators, but if you ever hear a rear brake rubbing noise,
have the rear brake linings inspected immediately. Rear
brake drums should be removed and inspected each time
the tires are removed for rotation or changing. Drum
brakes have an inspection hole to inspect lining wear
during scheduled maintenance. When you have the front
brake pads 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.
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