GMC 2007 Acadia Owner's Manual page 380

Driving on Grades
Your vehicle is designed primarily as a passenger
and load carrying vehicle. If you tow a trailer,
your vehicle will require more frequent
maintenance due to the additional load. Because
of the added load of the trailer, your vehicle's
engine may overheat on hot days, when going up
a long or steep grade with a trailer. If the engine
coolant temperature gage indicates overheating,
turn off the air conditioning to reduce engine load,
pull off the road and stop in a safe spot.
Reduce speed and shift to a lower gear before
you start down a long or steep downgrade. If you
don't shift down, you might have to use your
brakes so much that they would get hot and no
longer work well.
On a long uphill grade, shift down and reduce
your speed to around 55 mph (88 km/h) to reduce
the possibility of the engine and the transmission
overheating.
380
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).
When parking uphill, turn your wheels away
from the curb. When parking downhill,
turn your wheels into the curb.
2. Have someone place chocks behind the
trailer wheels.