when a/c is turned on i geta very loud vibration on my 2001 santafe

its the pully or the a/c pump.

is this common? it seems if i have it in drive with the e brake on if you push up on the exhaust btween the head pipe n the rest of the system it stops

ok well that makes things more complicated. so it doesnt matter if the a/c is on or not? or does it only happen when a/c is on. but since you did your own diagnosing sounds like you found the problem. you got the general area so now pin point it. might be loose bolt. or plastic underbody cover touching the exhaust etc.

yea the joint do you know if it has a bushing or gasket i called my hyundai dealer for a diagram but they said they could not give it to me because i was not a dealer?

ah that i dont know because i cant really picture what you are describing. but most likely a bushing and not a gasket. but most likely if you show up to the dealer and ask for the part they will show you a picture of what you will need. (pretending like your going to buy it on the spot might help)

yea thanks showing up with money usualy helps