1994 Geo Prizm 2 loud booms from front end

Recently, my son was driving the car referenced above. The front end made loud noises and the car locked up and would not shift into gear. After two days, I had it towed to repair shop and it started shifting and working again. The repair shop could not determine the problem, since it was working. I picked up the car today and test drove it all day. Once it warmed up after driving it frequently, the front end made two loud booms and it sounded like something was going to fall out. I immediately parked the car and left it. The gears did not lock up. I'm not sure if it is transmission, fuel filter, or what the problem could be. Is there any type of repair shop that can run a diagnostic on a 1994 Geo Prizm? Any ideas?