One problem related to power assist brake has been reported for the 1998 Chevrolet C2500. The most recently reported issues are listed below.
The problem seems to be a vacuum leak in the power brake assist unit . There is a clearly audible hissing sound when the brake pedal is depressed while the engine is running, stopping power has diminished by approximately75% with the ability to stop quickly { in less than 100 feet} virtually nil. This problem developed without any warning or signs of gradual failure. At the onset of the failure I was pulling a trailer equipped with electric brakes,for the remainder of my trip I relyed heavily on the trailer brakes to safely come to a stop. With out the trailer to assist me stopping the vehicle was extremely difficult and un relyable. Thank you.