How to solve the Mystery rattle at 110kph?
 

It's a light rattle sound, almost like a vibration, but not quite as evenly harmonic. It's not present in town, seems to happen regardless of wind direction, or speed of airflow over vehicle (headwind/tailwind seems to make no difference). It starts to materialize around 100-110kph, intensifies around 120 or so and sticks around at all speeds above 120... It's faint, and can easily be drowned out by the stereo, even at moderate volume, but it's one of those things, that once I've heard it, It's ALL I CAN HEAR now... Supremely annoying.

I've touched, pushed, jostled and tried to stop everything I can touch within reach of the driver in an attempt to find the rattling part. It seems to be coming from the passenger side, dash area, sounds like the glovebox... I removed all contents of glovebox, held the glovebox closed, open, pressed on pieces inside, outside etc trying to Identify the rattling part, but no luck. I've opened the cup holder, held it in place, emptied the "card holder" beside the cup holder, had someone hold the Cup holders in the back seat trying to eliminate any of the obvious, and likely sources of rattles and no luck yet... HELP!!!! It goes away at slower speeds, but any type of highway driving it materializes again... Gear selection makes no difference, it's there in 3rd, 4th, 5th, 6th, and while in Neutral coasting... Any Ideas? The car is a 2004 A4 Quattro 3.0 6sp manual Sedan with the Premium package, Cold package and Sport package, it has 77800km on it. So far, (other than this rattle) in very good condition, all stock.

Thanks!

Re: How to solve the Mystery rattle at 110kph?
 

I had the exact same problem and my investigation revealed one missing dash mounting screw from behind glovebox on the center console side. The screw went missing after a dealer service event. It was not the first time I received one of my vehicles back after dealership warranty work with less parts on the vehicle as compared to when I took it in.

This is one of the biggest reasons why I now service my own vehicles ;)

Re: How to solve the Mystery rattle at 110kph?
 

OK, good advice, thanks! I'll check that out. (I assume you had to take the glovebox out to get at it?)

The only service performed at the dealer was related to an AIR BAG warning light. If the sensor, or any other part they replaced is located in the dash, I can see how this could have happened. The noise materialized post service...

Re: How to solve the Mystery rattle at 110kph?
 

The Airbag controller is inside the dash ;)

Yes, you have to remove glove box to get at dash mounting screws.

The rattle could also be as simple as re-adjusting the dash mounting screws to shift the dash tension against related components like glovebox door and center console.