I have a 2002 Silverado 2500HD that is making a strange noise (high pitch) which appears to be coming from the drive shaft area. The noise starts as soon as I put it in drive and then appears to fade away, once I get up to a certain speed and then returns again when I slow down. I don't hear the noise in reverse. Someone mentioned to me yesterday that the CV joint may need to be greased. Not sure if there is a grease fitting for this. Does anyone know? Could it be the CV joint causing this? Does anyone have a idea as to what it would cost to get this fixed by a service center?