i cant tell which one it is and i dont wanna pull bolth apart if its only one . when im driving i take my foot off the gas it clicks and bangs really fast only when i decelerateit dosnt do it on truns but if i crawl under there and turn the yoke on the rear diff by hand till it stops and try to spin it more it goes a little bit more . the u joints are fine . when i go from reverse to drive it clunks bad drive to reverse is fine any ideas ?