when i start my quad up the plastic thing on the side the has the transmission in it vibrates when u start the quad up or rev it down my dad thinks its a chain but i would like to know if its something else

 

what is the make and year of your quad. if it's out of warranty you could just take the clutch/trans cover off and see if theres something broke or loose. my father in law recently got a 94 polaris explorer 400 and it also had a vibration noise coming from the clutch/trans area and it ended up being the cover was not on correctly due to the previous owner putting a new belt on before he sold it. hopefully in your case it is just something simple also too. goodluck and welcome to the forums

 

its a 96 and its a chain drive and thank u