One problem related to axle shaft seal has been reported for the 2003 Chevrolet C/k 2500. The most recently reported issues are listed below.
Took vehicle to dealer twice with complaint of parking brake non functional. Allowed truck to move fwd. When parked on incline,prk brake pedal fully depressed. Supposedly brakes adjusted twice,problem never better post dealer shop visit. Took it to private shop. Found to have pads soaked with differential fluid from rear end seal failure. Most probable cause of emergency brake failure. On discussing with mechanic, he mentioned this is a known common failure on these units. Paid for repairs myself. Never submitted for warranty repair to the dealer or to the ext. Warranty contract company (autogap xtend). Problem is fixed now. Seals ,old pads, repair receipt are in my possession.