2004 S10 Blazer rear Banging noise

Hope Someone can Help

Just bought a 2004 s10 Blazer 4X4 from a chevy dealer .What the dealer said about this noise ?????????
Their is a loud banging noise when you are going in drive about 15 mph and the tach 800 and you are going up or down a small incline and apply the gas quickly (not Hard) I hear a loud banging , once I go past 20 mph I can not make it bang .

check make sure wheel or wheels arn't loose. could be a strut or a pinion bearing or unaversal joint. but i'd pull that wheel off but first shake it side to side and in and out at top of wheel see if theres play in it.

I agree with scrapper. Try putting it form reverse to drive and tap the gas with your other foot, and then back to reverse. Is that noise there?

sounds like a worn leaf spring bushing or universal joint