GM Service Manual Online
For 1990-2009 cars only
  1. With the engine running, shift the two-speed rear axle into low. To be sure it is in low, you will need to move the vehicle in gear just a little.
  2. Hold the regular brake pedal down with your right foot.
  3. Apply the parking brake.
  4. Shift the transmission to NEUTRAL for manual transmission or PARK (P) for automatic transmission.