One problem related to transmission fluid leaking has been reported for the 2002 GMC C1500. The most recently reported issues are listed below.
On Dec 8, 2003 I was driving at approx. 45 miles per hour when my transmission shifted out of gear and then after a few secounds it shifted into low gear, all on its own. There was a car traveling behind that almost hit me from behind. I pulled over and put my truck in park. I looked under my truck to see if any thing had come apart. I did not see any fluid leak or any loose parts. I drove my truck to the dealership in low gear. They took my truck in for repairs (38,127 miles). I was 2,127 miles out of warranty. The transmission was repaired and it cost $1,057. 19. Today 3/30/05 on my way home from work the transmission does the same thing. I only have low gear and no reverse. This time I was lucky that no one was behind me when it happened.