I recently obtained a pair of nice used taillights for my 88 745, to replace the faded originals. While installing them I discovered an extra bulb, rolling around loose in one of the compartments of the old left taillight. Due to the colored plastic of the lens, it was just about impossible to see from the outside, so I had never noticed it before. It was plenty loud bouncing around inside the light. If you have a mysterious rattle coming from the back of your wagon, this would be worth checking out. With a sedan, you are unlikely to hear it, as the back seat seals off noises from the trunk area pretty effectively.