"tick-uh" sound on 5kcstq

[Wallace White <whitew@leland.Stanford.EDU>]

Driving my new 5kcstq around the last few days, I've noticed a ticking
sound. At first I thought it resembled the bad exhaust gasket noise on
another car I drove, but then I realized that it's not engine-speed
dependent. At 40 mph or so, it goes "tick-uh" around 5 times / second,
tick-uh-tick-uh-tick-uh. It's not loud--you don't notice it with the
windows up. It's only really noticeable when there's something like a wall
to reflect the sound back.

Any guesses? Hopefully it's nothing to worry about before a big trip? TIA.

- Wallace
  '87 5kcstq 138k