Rear Vibration when taking off from a stop AND turning

Explorer rear vibration when taking off (as in from a stop)
and turning, but only when on a slight incline going up hill. If it is on an incline going up and I accelerate going straight up the incline there is NO vibration. Happens whether a right or left turn. Doesn't seem to do it when the truck turns left or right from a stop on level ground.