we have replaced the rear tail lights and brake lights and turn signal..

The tail/turn on this car uses a dual filament bulb (1157) so ground issues are not the problem. With a test light and the 4 way hazards on, carefully check for power at each of the terminal contacts at the bottom of the socket. If there is power, change the socket, if not, there is a broken wire somewhere between the steering column and bulb. The first thing to check is if the car has had trailer wiring installed. Trace back the trailer wires to where they are spliced into the car's wiring. The blue crimp connectors tend to rot wires. If not, it will take a little time to trace the problem through the electrical system.