As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF AND GEAR SELECTED UP, HAD A HIGH FREQUENCY THUMPING NOISE. RETURNED TO SFO. WHEN SELECTED GEAR DOWN NOISE WENT AWAY. FOUND NOSE LANDING GEAR STRUT BONDING STRAP BROKEN. INSTALLED NEW TERMINAL END ON NLG BONDING STRAP AND RE-SECURED.