Unlikely that this situation happened though.
Blimey do I hope so, especially since the OP said
the same occurred on the return leg
and our QRH says in the event of needing a stall recovery "During liftoff if flaps are up, call for flap 1". (
AFAIK that part of the procedure is to cater for an accidental flapless
liftoff. FWIW we don't do flapless takeoffs or Flap 1 take-offs and I'm not sure if any 777 operators do).
....So I'll very much stick with the noise/rumble being shimmy or of similar origin.....
(Edit to add: A couple of points:
The OP mentions SIN. Without wishing to offend the locals 02C/20C at SIN isn't the smoothest runway in the world and it can certainly give the nose gear a good work out at higher speeds, and often makes for a noisy first few seconds after liftoff
Secondly many operators use or are moving to the use of "improved climb" for take-off performance, which may well mean increased ground speeds before rotate than under previous methods. That in turn may well lead to an increase in gear noise levels during retraction).