when i bought my 07 JKUX less then a year ago, i remember noticing- with the clutch pushed in you barely knew the engine was on! ater cutting the exhaust and having a cherry bomb welded into the exhaust pipe i noticed that 1st gear makes the entire jeep shake rattle and roll. upon re-installing the cherry bomb, we didnt miss and support hinges or anything.... this cant be normal....right????

 

It could just be resonation from the exhaust, or the exhaust rubbing on something causing a vibration.