You can find a place to do it locally or you can buy a new one from Tom Woods.
I paid about $175 for new u joints and a dynamic balance locally.
Tom woods is good stuff but about $500 ish
Was the truck recently lifted?
I had my rear DS die almost instantly after lifting the truck from a busted up stock suspension to an OME Heavy. Once the pinion angle changed it started vibrating as the "home" position of the U-joints changed.
New u-joints and a dynamic balance fixed it. It...