GMC Sierra Classic 2007 Owner's Manual page 620

(e) Make sure the safety belt reminder light and all
your belts, buckles, latch plates, retractors, and
anchorages are working properly. Look for
any other loose or damaged safety belt system
parts. If you see anything that might keep a safety
belt system from doing its job, have it repaired.
Have any torn or frayed safety belts replaced. Also
look for any opened or broken airbag coverings,
and have them repaired or replaced. The
airbag system does not need regular maintenance.
(f) Lubricate all key lock cylinders, body door
hinges, hood latch assembly, secondary latch,
pivots, spring anchor, release pawl, tailgate hinges,
tailgate linkage, tailgate handle pivot points,
latch bolt, fuel door hinge, locks, and folding seat
hardware. More frequent lubrication may be
required when exposed to a corrosive
environment. Applying silicone grease on
weatherstrips with a clean cloth will make them
last longer, seal better, and not stick or squeak.
(g) Check vent hose at transfer case for kinks and
proper installation.
620
(h) Change automatic transmission fluid and filter
if the vehicle Gross Vehicle Weight Rating
(GVWR) is over 8600 lbs or if the vehicle is mainly
driven under one or more of these conditions:
− In heavy city traffic where the outside
temperature regularly reaches 90°F (32°C) or
higher.
− In hilly or mountainous terrain.
− When doing frequent trailer towing.
− Uses such as found in taxi, police or delivery
service.
(i) Drain, flush, and refill cooling system. This
service can be complex; you should have
your dealer perform this service. See Engine
Coolant on page 498 for what to use. Inspect
hoses. Clean radiator, condenser, pressure cap,
and filler neck. Pressure test the cooling
system and pressure cap.
(j) A fluid loss in any vehicle system could indicate
a problem. Have the system inspected and
repaired and the fluid level checked. Add fluid if
needed.