Hello fellow benzes, my driveline makes a clunking sound as it hits the trans tunnel in low rpms, but is totally non existent at any other speed. This started after I replaced the trans mount, and there was a plate that went between the mount and the crossmember, does anyone know if this is factory? Maybe spacer to even out sagging old mount?

I'm hoping this is not related to center driveshaft mount problems, both flex-discs look pretty new.