There is a slight, not constantly, grunt in my Jeep KJ 3.7 2006, _not_ from wheel, suspension, belt tensioner or brakes.
This noise is also heard when the car is stopped.
It also sounds -not always- for a couple of seconds when I turn off the engine.
If anyone knows what it is let me know please.
Thank you!

(*) could the gas pump be a possible cause?