GMC 2003 Yukon Owner's Manual page 313

Here are some things you must not do if you stall, or
are about to stall, when going up a hill.
•
Never attempt to prevent a stall by shifting into
NEUTRAL (N) to "rev-up" the engine and regain
forward momentum. This will not work. Your vehicle
will roll backwards very quickly and you could go
out of control.
Instead, apply the regular brake to stop the vehicle.
Then apply the parking brake. Shift to
REVERSE (R), release the parking brake, and
slowly back straight down.
•
Never attempt to turn around if you are about to
stall when going up a hill. If the hill is steep enough to
stall your vehicle, it is steep enough to cause you to
roll over if you turn around. If you can not make it up
the hill, you must back straight down the hill.
Q:
Suppose, after stalling, I try to back down the
hill and decide I just can not do it. What should
I do?
A:
Set the parking brake, put your transmission in
PARK (P) and turn off the engine. Leave the
vehicle and go get some help. Exit on the uphill
side and stay clear of the path the vehicle
would take if it rolled downhill. Do not shift the
transfer case to NEUTRAL when you leave
the vehicle. Leave it in some gear.
{
CAUTION:
Shifting the transfer case to NEUTRAL can
cause your vehicle to roll even if the
transmission is in PARK (P). This is because
the NEUTRAL position on the transfer case
overrides the transmission. You or someone
else could be injured. If you are going to leave
your vehicle, set the parking brake and shift
the transmission to PARK (P). But do not shift
the transfer case to NEUTRAL. Leave the
transfer case in the 2 Wheel High, 4 High or
4 Low position.
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