Setup, age of rig, model, which end of the shaft, all would help. But for starters, I'll mention that I've had trouble with high mileage Chrysler 8 1/4 rear ends when the pinion yoke wears out. There are little ears that hold the caps tightly at the end, and they can wear out. When that happens, even a little, no matter hot tightly you sock down the straps, the caps will push out a little, and then the joint will hammer itself to death. Don't pinch pennies and recycle the straps. New ones are designed to stretch a little when you tighten them.