I am getting intermittent "clunk" from under middle of van
while driving.  '84 Vanagon, 1.9L engine, automatic
transmission.  "Clunk" not associates with turning as would
happen with CV problem.

Increasing occurrences of the"clunk."  Nothing obvious under
van.  Had my Son jump up and down on front bumper while I
locked at front suspension with wheels first turned full
right and then full left. Nothing appeared loose.

Got under middle of van.  Tried to push up on gas tank.
 Seemed secure.

Had Son drive van to end of driveway where the curb drops
off more than most driveways would.  Had him run van back
and forth over drop off.  No clunk.

Any ideas where I should look next?

Thank you,

John