I have a 01 suburban, I noticed today at a stop that there was a vibrating sound, I put it in P,Nand the vibration went away. accelerates smooth shifts fine no vibration while driving . While it was at a stop the exhaust sounded louder with vibration. I turned truck off, turned it back on put it in drive and no vibration. Iam clueless ??

 

I read somewhere else that it could be a balancer in the muffler . Any thoughts ?

 

You may be thinking of a resonator.

 

So would that give off a vibrating sound ? Can feel it in the floor a little. But the exhaust wad louder. Iev turned truck off n on drove it, and it's gone no vibrating sound or feel exhaust is normal sounding . Motor doesn't move when revved up while in neutral or in gear. My 1st thought was motor mounts . Shifts great while driving no lack of power. 2nd thought was tourqe converter. Idk ?

 

You may be confusing the "vibration" with the engine shaking/missing.
I'd check Plugs/Wires and Injectors.

 

Idk the rpms never changed idles smooth . The sound was coming form right side in front of rear wheel.

 

And it only did it in drive and at a stop with foot on the brake.