Fluid Recommendation
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2003 GMC Savana Special, 2003 GMC Savana Camper Special, 2003 GMC Savana, 2003 Chevrolet RV Cutaway, and 2003 Chevrolet Cutaway. However, it is still accessible from the selected car via links, so may be relevant.
Use SAE 75W-90 Synthetic Axle Lubricant (GM P/N 12378261; Canadian P/N 10953455) or equivalent meeting GM Specification 9986115.