Yes: I did test drive before I bought, and I herd the noise ( you couldn't miss it) but I thought it could be fixed.
Not knowing a lot about the Slingshot except for a blog I followed back in 2014 . He never spoke of any noise that I remember. In fact I complained to the dealer the day I got my 2015 and they took the rear axle apart and inspected and put new lub. It was good for about 10 miles and the noise was there again. Perhaps I'm making a big thing out of a problem that is unsolvable.
I do thank you for your time and have a great day