Subwoofer 3rd Brake Light Rattle
 

I recently put a custom box in the trunk and couldn't help but notice the rattle that comes from the 3rd brake light every time the bass hits. Didn't know if anyone else had the same problem or a possibly remedy

Honestly not trying to be rude. I was going to put a system in the car but decided it rattles enough on its own.

There are tons of threads on this. The easiest fix is to wedge something in between the brake light and window. I wound up removing mine completely.

Here's the latest thread going on now: http://www.ft86club.com/forums/showthread.php?t=35072

Take the third brake light out and move the light into the same place the reverse lights are.

If the rear window was tinted they may have loosened/broken the third brake light cover.

If you take the cover off the third brake light assembly you can probably get a thin layer of deadener in there or at the very least use a deadening spray. There's a thread around here somewhere for how to take it apart.

I had the same rear brake light on my WRX and with a system it rattled as well unit i put dynomat in the trunk and a little under the brake light unit and the problem was gone, here is their website, they also sell it at best buy.
http://www.dynamat.com/