I had replaced my rear struts about a year ago. One side has developed a bit of a knock or rattle type noise over uneven surfaces. I looked it over well and can replicate the noise with the tire off, car in the air, just lifting gently on the hub. Its coming from the top of the strut where its connected to the car. Top bolt and bolts mounting to the chassis are solid. The only thing I can think of is that maybe the 'top hat' was installed with the wrong side facing out. I don't recall how accurate I was reassembling exactly as disassembled. Could this be the issue?

 

check and see if you can wiggle your spring around and if it is loose.. maybe your sock is blown or you need to tighten the bolt on the tophat maybe?

 

Checked it out last night and the spring seems solid. all bolts on top tightened right down. It sounds like a light tapping and only evident over the most minor unevenness. anything that causes any real piston action is mostly silent.. Seems like the piston is just rubbing something in the top hat wrong...