1989 Mercury Marquis Strange noise at rear of car.

I have a 89 MGM and everytime I shut the engine off a strange noise comes from underneath the rear of the car near the wheels. Im guessing it might have to bethe motor in my load leveling shocks. Sometimes you hear it on 1 side sometimes the other or sometimes both sides behind both wheels. It got to da point where iI have to disconnect my battery everytime I leave my car because it drains all the power. Do you have any suggestions on what the problem may be.