Squeaky coasting and back pedal I recently bought a bike overseas rather than at LBS (no LBS had the type of bike I wanted).  Now the bike makes a strange noise and I can't bring it in for servicing (buy from LBS when you can!).  Could anyone give me any pointers to what could be the cause of this?

When the chain is on the largest (size 34) or second largest cog and I am either free wheeling or back pedaling, there is a squeaky sound.  When the chain is on any other cog there is no so such sound.  Visually, there is no contact of any part where contact should not be. 

Below is a link to a video.  What could this be?

Thanks,
Mark

 video recording of the behavior and sound
It was the freehub; when it is pulled away from the wheel while turning it makes the sound.  I guess putting the chain on the largest cog makes it pull the freehub slightly out. 

I have not solved it yet: this freehub apparently needs a 11 or 12 mm hex key to be removed rather than 10 mm and 10 mm is the biggest I currently own.