New 08' 1500 extended cab with 6.0L vortec and max trailering package.. On startup I hear rattling (sounds like lifters) for about 2 or 3 sec before the sound goes away.. I realize this may be lack of oil to the valve train and some rattling can be expected until it gets oil pressure but I'm wondering if this is "normal" for this engine? or do I have a problem... Oh, the vehicle has 2,400mi. and was broken in properly, etc. etc.