Vibration behind dash at 80 mph and above

[John W Cane]

We are the new owners of a 2002 TBird with 9000 miles. At 80 and above there is a vibration behind the dash, in the middle, which becomes louder and softer in absolute synch with road noise from the tires. It is what I believe is called a sympathetic vibration, a loud rattling/buzzing sound that is quite annoying. It only kicks in when the car is doing 80 or better.

Car goes into the shop next week. Will begin with a test drive, possibly preceded with removal of some cosmetic skin from the dash to allow the tech. to touch and feel around for the source while I drive at speed.

Wondering if there is any history of this defect.

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[George]

Whoh Johhn stop!!!!! Most likely it is the cabin filter installed wrong. Look up on the search function and see what you can find first. You may save a lot of money.😕
Check your owners manual for location, in center of cowl under hood

 

[George]

Some more info I found for you, hope these help:

There are the push pins in the center of the main plugs that hold the filter cover in place. Take a small screw driver and push the center of the pin downard and then lift out the entire plug. You will then be able to lift the cover up far enough to slide the old filter out. There is no need to remove the entire plastic cover, just lift on the left side of it and pull out the filter.
There is a tab on each side of the filter. Just lift each tab on the left and right and the filter will slide out of the slot it is in. Reverse this process when installing the new filter.
The plastic cover must be snapped back into place on the firewall side and the rubber molding strip on the windshield fit flush with the windshield.
It should only take about 10 to 15 minutes to do the whole thing.
George, I would take out five clips. Just makes it a little easier. And it is on the passengers side.
OTHER INFO FOUND:
The trim at the base of your windshield. It's not seated properly and probably happened the last time someone changed the the cabin air filter.
To fix - take that trim partially off - you'll need to carefully remove the buttons holding the trim down (you'll need to lift the hood to get to them.
Then reinstall the trim so that all the clips on the underside of the trim are properly clipped in. Not sure how many clips you'll have to reseat. Once those are in place, the trim along the windshield should fit flat against the windshield and your buzz should be gone. (the speed at which the buzz occurs is the giveaway as to it's cause)
And more:
Check the rubber molding at the bottom center of your windshield, it may not have been properly installed when they replaced the windshield. I noticed a noise at freeway speed and could actually see it moving to the sound of the noise. I just added a bead of silicon and the noise stopped.

Check to see that the trim at the base of your windshield is laying flat against the windshield all the way across the whole windshield. If there's any gap at all, it will vibrate at high speeds (around 80) - and you really can't tell where the sound is coming from. If there's a wind out, it'll vibrate at lower speeds (60-70).

One is filter and one is filter assembly - One is the whole thing, the other is just the element:

OE Number XW4H 19N619 AB
OEManufacturer Ford
OE Number XW4Z 19N619 AC
OEManufacturer Ford

By the way John, I had mine replaced by Ford dealer for $25.00. Before they did it I warned them that if not done right it would vibrate. They already knew that.