A couple of weeks ago, I noticed a slight creaking noise that seemed to be coming from the rear end when I put the car in reverse. The noise is now much louder - it's not screaming loud but still substantial. Any idea what this is? I'm pretty sure it's coming from the rear.
NB: I have one really bad ball joint on the front driver side and one pretty bad ball joint on the front passenger side. I know that this can cause creaking, but it's odd because the noise only happens in reverse and seems to be coming from the rear end.

Another question: I'm going to fix those ball joints (that is, I'm going to find an independent mechanic here in PDX to help me fix them) hopefully sooner rather than later - is there anything else that is worth replacing while doing this job? It's an 83 with 293,000 and not a whole lot of records. I wouldn't be surprised if none of the other front end components (except the front shocks, which were replaced a few months before I bought the car - don't ask me why the guy did the shocks and left the joints in the condition they're in) have ever been replaced (the ball joints are original) - so is it worth it to replace some other stuff while I'm at it? The car actually feels pretty tight while driving but there's a lot of movement in the tires when I shake them and it definitely feels a little loose on the highway.

Thanks