why does it make a cracking sound?

[PsSsShTGSX]

i just got my eibach pro kit put on today. im using stock struts and never had a problem with them before. anyway, if i hit a bump while driving at a decent speed i hear a loud crack coming from the rear driverside wheel well. if i hit a speed bump at a lil over 5mph to make it bounce, it will also do it. it makes the noise as soon as the wheels leave the bump and touch flat ground. any ideas as to what it is? im gonna take it back to where i got it done to have him look at it, but im just currious so i know until the weekend is over.
thanks,
chris

 

[ECLIPSE4x4]

so did you find out what it was?

 

[PsSsShTGSX]

yup. he forgot to tighten the nuts that come up through the trunk.

 

[ECLIPSE4x4]

nice job..... tool j/k