i have a weird whining and sometimes like almost a loose sounding clank(if that makes any sense) i really notice it when letting off the gas around 30-40mph, it sounds like its coming from the rear end, my car is pretty much stock (just a borla cat-back and lid) any help?

 

any one?

 

It could just be the pinion gear bearing (crush sleeve)...or it could be that you're rearend is about to take a dump.