GM Service Manual Online
For 1990-2009 cars only
  1. Start the engine and operate the vehicle for 15 minutes or until the transmission fluid reaches an operating temperature of 82-93°C (180-200°F).
  2. Park the vehicle on a level surface.
  3. With your foot on the brake, move the shift lever through each gear range. Pause for about 3 seconds in each range, ending in PARK.
  4. Apply the parking brake and let the engine idle for 3 minutes.
  5. Remove the transmission fluid level indicator. Wipe the indicator clean. Insert the indicator. Give the indicator a full twist in order to close.
  6. Wait 3 seconds and remove the indicator.
  7. Read both sides of the indicator. The fluid must be within the hot cross-hatched area using the lowest level reading.