Four months and 1300 miles since last oil change. Oil level ~3/4 full, oil pressure normal (40 psi cold, 20 psi warmed up at idle).
All fluid levels good, alternator, ps, and ac quiet. Noise did not occur after sitting overnight. Noise duration is too short to track down.
Noise is closer to a light tapping, definitely not a heavy thump. Similar to an exhaust manifold leak, but not as loud.
Noise does not happen every time. More likely to occur after the truck has been sitting a few days.
Ed B.