In a message dated 98-07-14 13:08:34 EDT, you write:

<< On Tue, 14 Jul 1998 08:53:01 -0700 Vernon Craddock said:
 >  When entering the wake of a Semi Truck while a cross wind is present, I
hear
 >the following:
 >whap       whap    whap  WHAP SLAM!

 well, even though you THINK it's coming from the rear, sounds can fool you.
 mine does that and i tracked it down to the FRONT headlight grill. yup.
 the turbulence of some big trucks, especially those with round tanker
 trailers or car-carrying trailers ("portable parking lots"), causes the
 bottom of the grill to flap around. >>

Had the very same problem with my '87.
Except this time it was the lower grill.
It seems that my local IVD (idiotic Volkswagen dealer) had repaired a dent in
the front apron by filling it with approx. 1 inch of Bondo instead of pulling
the dent out.
This extra 1 inch of material prevented the 1/4 turn fastener from securing
the grill and allowed it to "flap".
It would make one heck of a racket especially when closing on semi's at 75 -
80 mph on the Interstate!

Sam Bateman
Fork Union,VA
'87 Vanagon GL   126,000 miles