*ting*

When I accelerate or let off the gas (at lower speeds ), I get a ting sound from under my truck. I can only hear it with the windows down. It sounds like it would as if I was tapping a ball peen on my tranny. Doesnt happen when coming to a stop. No problems otherwise, just wondering if its something I should really look into or if I should just crank up the stereo .

-I checked the torque on my ubolts
-checked all bolts on driveshaft
-clutch engages perfect, shifts like it should

Thanks