Car just started randomly grinding in reverse tonight. Does it when not moving if i hold brake aswell. I can feel it in the shifter and when i go over bumps. Ive yet to jack it up and check but only thing that comes to mind is somehow out of nowhere the downpipe is hitting the firewall. How after being fine for a month since the trans swap idk. I cant hear it from outside. All my mounts are poly so its not like they could of collapsed.