>The noise is low-frequency and it reverberates throughout the bus. I can't
>tell where it's coming from, it depends which way I turn my head.  The
>noise begins precisely at 43 miles per hour, and increases in frequency and
>volume the faster the bus goes. It doesn't grind; it's somewhere between a
>hum and a sustained moan. There is a vibration to it but the vibration is
>tactile, not aural; you can only feel it.

Ken, my Vanagon makes a sound just like this when I have my canoe on
top. I found the source of the sound to be the wind moving across the
front hold down strap on the canoe. It too starts at about 40 mph and
grows louder with speed until at 55 you and the passenger can't even
carry on a conversation without shouting. In my case, the cure was
moving the strap back about 6 inches.

You might look for something that is flat and catching the wind. On a
VW van, this should be easy.  ;-)

Doug Skinner from Bowling Green, Kentucky
85 Vanagon GL
debug@wku.campus.mci.net