After a visit to the car wash I drove my FJ Cruiser off and discovered that the rear end was locked in (dash light flashing). The car wash guy must have accidently pushed it when cleaning. I drove approx. 3 or 4 miles on dry pavement at approx 40 mph. What harm if any has occured. Do I need to worry? I know I should only drive at low speeds (5 mph) when using the rear locker.