clunking noise during auto-shifting
 

Today my chevy dealership informed me my clunking sound during the 1-2 and 2-3 shift points is a normal acceptable problem according to GM. My truck is a 07 Silerado 5.3
They say the overlap of the clutches releasing in the auto transmission causes this clunking sound and they say mine is quiet compared to others like my truck. I said to them 'bull crap", people turn and stare at me in shopping malls when this truck shifts from 1-2 at low rpm's after they hear the Klunk sound. I believe it's my ring and pinion play ( I have .250 play at the pinion, or it could be a worn shaft on the spider gears.....
Oh yes, my drive shaft is aluminum, no yoke, and i have check my universal joints.