[Ak Sourdough]

That inner ball, or cover as you called it must be in there. That ball is what the rear axle pushes against to move the car forward. Without it there is nothing to push against, the torque tube ball has to have the inner ball to push against. I would think that you could feel the torque tube hammering and bouncing around in there when you drive the car. Perhaps the driveshaft is pushing against the u-joint to move the car, but you absolutely need that ball in there.