Parking On Hills - GMC Sierra 2005 Owner's Manual

When towing at high altitude on steep uphill grades,
consider the following: Engine coolant at high altitudes
will boil at a lower temperature than at low or near
sea level altitudes. If you turn your engine off
immediately after towing at high altitude on steep uphill
grades, your vehicle may show signs similar to
engine overheating. To avoid this, let the engine run
while parked, preferably on level ground, with the
automatic transmission in PARK (P) for at least
five minutes before turning the engine off. For manual
transmissions, let the engine run while parked,
preferably on level ground, with the transmission out of
gear and the parking brake applied, for at least
five minutes before turning the engine off. If you do get
the overheat warning, see Engine Overheating on
page 5-37.

Parking on Hills

CAUTION:
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You really should not park your vehicle, with a
trailer attached, on a hill. If something goes
wrong, your rig could start to move. People
can be injured, and both your vehicle and the
trailer can be damaged.
But if you ever have to park your rig on a hill, here's
how to do it:
1. Apply your regular brakes, but don't shift into
PARK (P) yet for an automatic transmission, or into
gear for a manual transmission.
2. Have someone place chocks under the trailer
wheels.
3. When the wheel chocks are in place, release the
regular brakes until the chocks absorb the load.
4. Reapply the regular brakes. Then apply your
parking brake and shift into PARK (P) for an
automatic transmission, or REVERSE (R) for a
manual transmission.
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