Springs, struts or control arm

In my 96 Seville, I have a squeaky noise coming from the back of my car on both sides.  The noise has gotten to the point that everyone can hear me coming down the street.  It sounds like something is worn.  The car also bottoms out when I go over large speed bumps.  Is this the springs, struts, control arm or all of them. 
 
Thanks 

Well first of all there are 2 types of squeaky metal to metal & bushing squeak. Does it happen from the car bouncing from bumps in the road or does it sound like its from the wheel rotating? As for bottoming out You might need struts (coil spring & shock combination) the coil spring might still be good but if the strut or struts havent been changed since factory you will need them replaced. Do a bounce test to it. Push the car down a couple times n if it keeps bouncing more than 2 times after you lift off of your car they are bad struts. Check your brake pads & rotors for any signs of scraping n splash guards too. Good luck

Also your car may have the automatic leveling system (but im not 100% sure) so see what it has first of all for rear suspension then proceed from there.

Thank you for the info.  I plan to replace the shocks and the springs, shocks first.  The car has the original parts on them and it has over 160K.  I am hoping that it will cure the squeaking noise, but if it doesn't it needs them anyway.  It sounds more like a brushing but I can't identify it.  Someone mentioned that it could be the control arm brushings.  I've checked underneath pretty good and it not the brakes.  As I'm driving it will squeak.  If its in park and I push down on the trunk, it will squeak.  When someone gets in or out of the car, it will squeak.  It definately has something to do with the suspension parts.  Do worn springs make squeaky noises?
 
Thanks again 

I can identify with your creaking/squeaking problem.  I had similar issues and it irritated me to no end. 
Read my reply in the following posting.
 
Hutch
 
http://www.cadillacforum.com/m_1984/tm.htm

If you push down on it and it sqeaks, that tends to be bushings either on control arms or the coil spring pad for the strut.

Cadillac is telling me that you can not replace the bushings on the control arms.  They are telling me that I need to purchase a new control arm for $250 each.  I can get them from the junk yard for about $40 each.  It looks like they sell brushings for the control arms but no one has them in stock.  Is the any way to lube those brushings or the coil shock pad.  If so, with what?
 
Thanks

Yeah Cadillac wants you to buy it as one piece because its easier to throw it away n replace rather than take it out and press out the bushing n press the new one in or its just a one piece deal from the start. My Moog book only shows Upper strut mounts for your vehicle, no bushings. So you either go with salvage yard or dealer for the whole thing

Thanks for the help!

I had the same squeak in the right rear suspension of my '99 DeVille Concours that about drove me nuts (and I have a big head start on that process anyway!).  I took it to the Cadillac dealer and they wanted to replace the entire assembly at some outrageous price.  I paid the $80 diagnosis fee and took the car home.  I jacked up the rear of the car, found some liquid silicone, aspirated some into a 5cc syringe, and using a 22 ga needle injected 1-2 cc of silicone into each bushing.  The squeaking instantly stopped. It's been several months now and still no squeaks, and there was no effect on the way the car handles.  I figured if the thing needed replaced anyway, what would it hurt to try my home remedy and risk having to replace it sooner than later.