Hello i have a gmc 2005 t7500 truck. I am having some type of issue when releasing the gas pedal the engine doesnt make make that brake air type noise when coming to a stop. It rolls like a car with no noise and sometimes it will have an air build up and make that engine slowing down noise. I do not have air brakes. Also when picking up off a red light it makes that a normal truck sound and gets quiet with a zzzzz sound.. Exhaust light on dashboard also goes off when warming truck up?
hope this makes sense