A clunk in the fuel tank is normal?
I'd ask if there was an informational service bulletin that stated that a clunk in the fuel tank was normal.
I mean, they have informational bulletins all the time for things like this bulletin, which may or may not pertain to your problem.
April 25, 2006
2003 and later Pilot-ALL
2006 and later Ridgeline - ALL*
Noise and Judder From the Rear When Turning
(Supersedes 04-040, dated August 13, 2005)
Updated information is shown with asterisks.
There is a noise and judder from the rear when turning.
The VTM-4 differential fluid is contaminated by clutch wear, condensation, or both. This causes the VTM-4 differential clutches to make noise and to judder when turning.
Replace the contaminated VTM-4 differential fluid.