There is another common problem with Luminas with the transverse, composite rear spring, like yours (and mine). The ends of the spring have rubber insulators from the factory where they contact the rear knuckle. One of mine is missing ('94 3.1) and the other is quite deformed and about ready to fall out. These are very easy to see if you look under the car from the rear - no need to jack it up. I also have some banging noise occasionally and I believe the missing rubber is the culprit. The aftermarket makes nylon or teflon end-pieces to replace the factory rubber ones. They are about $25 each and are supposed to be much better than the rubber ones. I ordered them and am going to replace mine as soon as I get some time.