I have a 2005 Sierra with 46000 miles on it. I have noticed a howl when I slow down for a stop sign. I do not have the big lug tires on so I dont think its tire noise. It sounds like its in fourwheel drive. The indicator light is on for two wheel high. I shifted it in and out of four wheel drive a couple of times. But that didnt help. There are no code lights or service four wheel drive lights on. Im going to jack up the front to see if a bearing is bad. Anyone have any ideas on this! Thanks Bruce

 

Check if your rotors are cracked or warped. Also check for play in your tires (lift the tire off the ground and try to wiggle it side to side)

Thats all i can think of that can make that sound