Thumping on the rear left side

I have a thumping noise coming from my 01 z28 dont know what the hell it si does anyone have an idea??? It more frequent the faster I drive. I have no clue im thinking its my shocks or struts no clue. its stock havent channged the exhaust just to find out what it is

I had a thump pulling into driveways and over big bumps. Turns out the passenger side spring had popped out of the spring isolator at the top of the spring. That could be your problem and a good place to check!

yeah i hear it all the time though now over bumps all the time