Noise sound from underneath truck.

I have a 09 5.3l chevy silverado. I have a noise that
sounds like a ting ting ting. From under my motor.
Sounds like its coming from the exhaust. I
disconnected the exhaust and could still hear the
ting. When i put the truck in reverse or forward the
ting ting ting gets faster the faster i go then if i hit
my breaks its tings faster till i stop. Now i was
thinking flex plate or torque converter. Maybe
starter
Drive shafts are tight. U joints are good. Looked at
flex plate teeth they all look really good. The thing
that gets me is that when i hit the exhaust that
crosses over my transmission the noise goes away
for a few sec then comes back. Im stumped can
anyone help me out.