Planetary Gearing
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Silverado, 2003 Chevrolet Cab & Chassis Silverado, and 2002 GMC Sierra. However, it is still accessible from the selected car via links, so may be relevant.
The planetary gear train includes 3 constant-mesh, helical planetary gear sets. By the engagement of the clutches in various combinations, the planetary gear sets act singular or together to provide 5 forward ranges, Neutral and Reverse.