GM Service Manual Online
For 1990-2009 cars only

Transfer Case and Front Axle (All-Wheel Drive) Inspection for Chevrolet Astro - 4WD 2003

Every 12 months, or at engine oil change intervals, check front axle and transfer case and add lubricant when necessary. A fluid loss could indicate a problem. Check and have it repaired, if needed. Check vent hose at transfer case for kinks and proper installation.