Global Machinery Company Sierra 1999 - Manual (Page 107)

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CAUTION: (Continued)
With four - wheel drive if your transfer case is in
NEUTRAL (N), your vehicle will be free to roll,
even if your shift lever is in PARK (P). So, be
sure the transfer case is in a drive gear
-- not in
NEUTRAL (N). If you’re pulling a trailer, see
“Towing a Trailer” in
the Index.
1. Hold the brake pedal down with your right foot and
set the parking brake.
2. Move the shift lever into PARK (P) position like this:
D Pull the shift lever toward you.