The Car: 1990 LX 5.0

The Issue: Whenever I drive at highway speeds (45 or highway), I start to hear a strange rattling noise coming from inside the dash. It sounds like it is coming from the tachometer or the speedometer. It does happen at lower speeds. I have no idea what it is, but it is very loud. Anybody have or hear about this before?? I would like to get an idea of what im looking for before tearing into the dash. Thanks for the help.

 

Probably just the speedometer cable,

 

it could be the cable or the speedometer its self, if it was the tack it would do it at any speed. the only thing i would say is try and pin piont it to one thing.

it ia hard to say without heering it.