Awful knocking in the dash

[CHE]

While creaks and rattles aren't always consistent from car to car, sometimes they are so I'm taking a shot. There is a horrible knocking noise coming from the front of my 98 cobra's dash. It's not the usual squeaks, rattles, creaks and groans that the car has over every inch of pavement..it's almost like as if someone is tapping a piece of wood in morse code. I haven't yet ripped the dash apart (it's that bad) and it doesn't appear to be coming from under the hood. Shot in the dark, but has any other stang owner come across this knocking and if so, solutions? cause? A lot of some kind of gasket material blew out the vents years ago..I don't know if that was the gasket that surround the vents or from something inside the car that buffered contact.

[nos4atu]

thats odd when does it happen? fan on/ or off certain speeds? or all the time.
maybe film it and post it so we can hear whats happening.sorry not much help but ley us know if you figure it out

[Cobradon]

My 96 cobra also knocks in the dash off and on and seems to be the speedo. It only knocks at low speeds around 5-20 mph. Don't know why though since it has electric drive instead of cable driven.