Crunching Thunking noise

Hi. I have a 91 Z24 and it's my first car. I don't know too much about cars but I can tell you I've had a lot of bad experiences with mechanics ripping me off. Being female has been my excuse but I believe being naive is too. The most recent problem I've been having with my car is this god awful crunching combined with thunking right under my feet on the drivers side. It's very inconsistent and doesn't seem to happen all the time.

Initially when I heard the noise I had my strut on that side replaced. When I was having it replaced (used a part from a wrecking yard) we noticed the drive shaft was broken in half literally. So I replaced it with one from a wreckers as well but now the noise is odd and we can't seem to figure it out. Has anyone had this issue?

I've had someone suggest its loose exhaust but it's not rattling and it's a very deep crunching/thunking combo noise. I can say it's driving me nuts and i'd really like to figure it out. Thanks in advance!