It could have popped in place like mentioned above but I would pull the CVA's out and check the silver pins that are press fit in them. These are the silver pins that run in the slots of the outdrives. Give them a good squeeze to make sure they are tight. My truck did that for about a month before I figured out that one of those silver pins was loose. It would slip out and catch the a-arm causing it to lock up. Before I saw what it was I was usually at the races and freaked out when I had it up on the stand spinning the wheels before running. As I would monkey around with the tires trying to spin them it would make a loud click and then it would spin and run fine. It never caused an issue while actually running (by luck/chance I'm sure). The silver pin doesn't completey fall out of the CVA and it doesn't slip/offset in both directions. It just slips from centered to one side and back but it is relativey stiff. It doesn't rattle around or back and forth when you shake it either.