Three problems related to transfer case have been reported for the 2003 GMC C2500. The most recently reported issues are listed below.
I have a 2003 GMC sierra 2500hd. The four wheel drive works intermittently. According to GMC document id#1400441 there is no fix for this problem now. However, they are working on the problem and as soon as a fix is available they will make the repairs in the trucks. This problem applies to 2003 and 2004 k series. These trucks are not only used personal but in some cases, also in emergency rescue and fire services where the 4 wheel drive may be needed to gain access to patients. I can be contacted for further details.
There was an electrical short in the transfer case that resulted in vehicle engaging into 2-wheel drive or 4-wheel drive by itself. Dealership replaced the failed part. Also, front driveshaft was loose, causing the front wheel to vibrate/shake.
The 4-wheel light illuminated on the dash board which indicated the 4 wheel drive was on, when it was not, the vehicle was at the shop on 6 occasions, and the dealer was unable to correct the problem.