Morris85 is correct about the wire colors off the GM headunit. But, the wire that is connected to the speakers are different //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif I know this because I had my 99 Yukon torn apart installing new crap today. If I remember.. Left Rear + is white, Left Rear - is Brown, Right Rear + is red, Right rear - is Brown. I'm not sure at what point it changes. I actually guessed assuming the brown is - on all speakers. Hopefully it is the same on your truck.