i have a 2001 silverado 1500 4.8L 4x4. i recently noticed that there is an audible whining noise when i press the gas. it only makes the noise when in gear and on the gas pedal. if i let off the gas pedal it stops. if i put it in neutral and rev it up it doesn't do it. any idea what this could be? i also had the abs light come on recently could have something to do with that as well?