Chevrolet Silverado Classic 2007 Owner's Manual page 454

When towing at high altitude on steep uphill
grades, consider the following: Engine coolant at
or near sea level will boil at a lower temperature
than at higher 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 a few 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 a few minutes before
turning the engine off. If you do get the overheat
warning, see Engine Overheating on page 506.
454
Parking on Hills
CAUTION:
{
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.