Popping sound when going in reverse on 1987 Honda Civic

I have 1987 Honda Civic (5 speed manual). I just replaced struts and shocks. When car in parked for a while (overnight or several days), when starting it and going in reverse, I hear a popping or snapping sound that seems to come from the rear of the car. Sometimes, there is a dragging or pulling resistance when I try to go in reverse until I hear the pop, then car goes in reverse. If car is going forward, there is no problem. This only happens when car is cold, parked for some time. If car is warm and I have been driving for a while, I don't have a problem starting it up and going in reverse. Any ideas???