> I chased several issues before finally fixing the "highway whistle" on my
> driver's door. It turned out that the felt channel (where the top and back
> edge of the glass rest when the window is up) was missing it's outer flap.
> That is to say, the "U" of the channel has a flap on each side to seal the
> glass, and mine was broken. Replacing that channel took all of 5 minutes,
> and now my cabin noise is greatly reduced...to the point where I can start
> worrying about all the *other* noises I can now hear!

 I had the same thing. The whistling mirculously vanished when I replaced
the top/rear felt channel. That little lip inside being there apparently
plays a critical role in noise reduction.
One "gotcha" to watch out for when replacing this is cutting it to fit. It
comes a few inches longer than necessary and I got a little enthusiastic
with the first one and "eyeballed" the cut by holding it up to the door.
Turns out it has a tendency to compress ever so slightly as you put it on
and also "fills the radius" at the back a bit more than it looks like.
Subsequently, my driver's side has a 1/8" gap now (argh). For the passenger
side, I ended up just putting it on "uncut" and spending 10 minutes or so
nibbling away at the far end a little at a time until it just fit.

--
John Bange
'90 Vanagon - "Geldsauger"