Lately I've been noticing more and more a rattling noise from the back when going over bumps and pot-holes. It sounds like it's coming from around where the rear speaker is on the passenger side. How do you tell if your springs are worn? What is the functions of the shocks themselves and the springs? Thanks for taking a look at this.

 

you can easily tell if a spring is broken: visually, if you noticed one side of your car looks akward, like its leaning to one side...that's an indication of a broken spring.
as for shocks the purpose of them is to control the ride confort
so like if you hit a bump the shock is suppose to absorb the impact..hench the name "shock absorber"....it's main purpose is to keep the wheels on contact with the road...while trying to maintain smoothness of the ride...
also it sounds like you may have a broken bushing in a shock absorber, if the bushing become real worn, what happens is that
the mounting point of the absorber will start hitting the body of the car....and you'll get alot of noise while hitting bumps and pot holes if you will...if anything you should get that inspected ASAP
because if this is the case, your gonna let the hole get larger,
because if the end doesnt stay stationary in it's place, its gonna keep jerking around in it's place and making the bushing holes much larger then what it's suppose to be....

 

With the car parked, stand at the rear and push on one side or the other, then push the rear down and let it spring back up. You should be able to reproduce the sound. If not, get under the car and start wiggling components.

The rattling in my car was from the wheel lock bouncing around the spare tire area.

 

check the mounts to your shocks and the bolts holding in your panhard rod. I just got rid of some nasty squeaks yesterday with some grease. your rear shocks might be bad too (mine were).

 

The rear shocks in the Iroc now are Gabriel Hi-Jacker air shocks. They are about two years old. Do you think they could have crapped put by now?

 

... there is also a rubber spacer on top of the springs that could be toast.