I got this 02 35th anniversary edition convertible with auto that came into work today with a vibration from 700-1100 rpm.It only does it in gear and I can only get it to do it when cool,once warm,it lessens.It is mainly heard in the interior,but you can feel it under the hood on drivers inner fender,like if you hold the AIR hose.
I set the park brake,dropped it in gear and used the TECH 2 to raise rpm til it would vibrate,then went looking.I do notice the drivers side part of the Y pipe seems to vibrate a lot,but applying pressure to it does nothing.
I did not find any loose mounts or x members.It seems like something harmonic,aybe in the convertor or low end of engine.
Has anyone had or heard of anything like this??Please let me know.
Thanx,Joe

 

Sounds like the air pump to me.