1995 525i Auto has a loud rattle in dash. Rattle present from 75 mph to 110. Sounds like nylon/plastic gears stripping/slipping. Instrument cluster pulled and disconnected- not there (I'll never pull that again while driving). Noise seems to be coming from behind/below the defroster ducts behind left side of instrument cluster. Pitch doesn't change with speed. When I place my fingers back there, can't feel any vibration. Any ideas?