I don’t know where else to post this, but here seems to best fit. 
Small sleeper truck (The size of a pigeon ) : (2 variants with the same issue.) Rear suspension breaks on spawn, drastically reducing handling at 60+ MPH
Small sleeper “economy” car: rear wheels fall off completely on spawn, limiting the car to ~16 MPH
I just created my account for the sole purpose of posting broken stuff, so unless the rules change or you can pm me for the files, Y’all can’t see the things.
Welcome to the forums… can you at least post pictures of the exact bodies you used? You can upload them to imgur or something and post’em here. Or better yet, you can also share your .car files from automation here as well.You can upload them to dropbox, drive, mega, etc… and post the links here.
Neither can we know what bodies and variants you refer to by calling them “small sleeper economy car”