Attached is an exploded diagram of the driveshaft assembly including the CV joint. The slip yoke has a ball cast onto the end of it that rides in a spring loaded split seat. If you have a lot of slop in your CV joint these parts are probably shot. Occasionally N.O.S. CV Joint repair kits show up on ebay or in Hemmings and other sources. This kit includes a seal, split seat, and spring. If your driveshaft tubes aren’t dented or damaged you might want to replace all the u-joints, repair the CV joint with the kit and have the driveshaft balanced at a competent driveshaft shop in your area. You should also check the center bearing and surrounding rubber cushion for any damage. And another source of vibration is the pinion angle on the differential.