Creaking rear shock or spring

Hello, I have a 1986 190E 2.3. I have been highly annoyed by a creaking noise that is coming from my passenger rear shock, spring, or wheel. (Don't know which) Anyway, I had been advised to go in the trunk, peal back the carpet and I will find a bolt that goes to the rear shock. I tightened the bolt but the noise will not go away. Well, I did this and noticed that when I wrench the nut on the bolt, the whole bolt and nut go around and around. I can't tighten it because it might but stripped, but, the drivers rear does not make the noise and the nut and bolt do the same thing when wrenched. This problem may seem confusing but it is making me nuts. Could anyone tell me what is the problem? I am installing H&R springs this week so I'm hoping that is the problem so when have them installed, the noise will go away. I have Bilstein shocks, but they are OE I think, not the yellow sport shocks. Again, the noise seems to be coming from the spring but I'm just not sure, also, I have lubricated everything I can find and that has not worked. THANK YOU SO MUCH FOR YOUR RESPONSES! Scott slchaffin@ou.edu