GMC 1997 Safari Owner's Manual page 100

Torque Lock
If you are parking on a hill and you don't shift your
transmission into PARK (P) properly, the weight of the
vehicle may put too much force on the parking pawl in
the transmission. You may find it difficult to pull the
shift lever out of PARK (P). This is called "torque lock."
To prevent torque lock, set the parking brake and then
shift into PARK (P) properly before you leave the
driver's seat. To find out how, see "Shifting Into
PARK (P)" in the Index.
When you are ready to drive, move the shift lever out
of PARK (P) before you release the parking brake.
If torque lock does occur, you may need to have another
vehicle push yours a little uphill to take some of the
pressure from the parking pawl in the transmission,
so you can pull the shift lever out of PARK (P).
Shifting Out of PARK (P)
Your vehicle has a brake-transmission shift interlock.
You have to fully apply your regular brake before
you can shift from PARK (P) when the ignition is in
the RUN position. See "Automatic Transmission" in
the Index.
If you cannot shift out of PARK (P), ease pressure on
the shift lever -- push the shift lever all the way into
PARK (P) as you maintain brake application. Then
move the shift lever into the gear you want.
If you ever hold the brake pedal down but still can't
shift out of PARK (P), try this:
1 .
Turn the key to OFF.
2. Apply and hold the brake until the end of Step 4.
3. Shift to NEUTRAL (N).
4. Start the vehicle and then shift to the drive gear
you want.
5. Have the vehicle fixed as soon as you can.