when driving a super sport silverado (automatic) is it ok to drive the truck using second third and drive shifting back and forth instead of driving it in the drive (D) mode at all times?

Hello dodgers13- Why you want to do that? This is not one of those triptronic transmissions which gives the option of automatic or manual shfting. The lower gears are intended for use in special situations, like descending or climbing a steep hill. Shifting the way you suggest would increase the liklihood that you would overload the transmission and damage your truck. I advise against it. Good luck from Bovan.