One problem related to automatic transmission cooler has been reported for the 2004 Chevrolet Silverado. The most recently reported issues are listed below.
I was driving home from errand running and found the brake pedal going almost to the floor. Found a puddle of brake fluid under the truck near the back of the cab and bed of truck. Called my service person and he said it was probably a ruptured brake line, and from the description of where the puddle was it was probably above the gas tank where the line is secured to the frame. He also stated that he has repaired multiple chevy trucks with the same problem. I have seen the underside of my truck and all the lines are rusted, including fuel and transmission cooling lines.