2004 crewcab and when I am idling the exhaust is like vibrating and u can hear and feel it in the cab. I know it's the exhaust because I can get someone to hold there foot on the tail pipe and it will stop. But I have no clue what to do to fix it

 

Its touching something solid like a shock or the frame or a crossmember ect. With the truck off give the exhaust a good shake you should be able to tell where it is hitting.

 

Mine always moves no matter how tight I get it and rubs on the transmission cross member. Crawl under the truck and have a look-see.