Startup noise

[uconnjack]

I am trying to troubleshoot a strange noise that occurs when I start my 2008 5.3L 4WD Avalanche.  It only happens occasionally, usually only on cold starts (although I can get it to happen with repeated startups), and it is usually pretty brief and goes away as the car starts.  Its a metallic noise but kind of hard to describe, so I have a video/audio of three repeated startups, and the noise occurs on the third turnover.  

 

My first thought was of course starter, but I am not sure if it would make this kind of noise, and it does not occur often or long enough for me to pinpoint the location of the sound.  Any ideas?  Thanks in advance!

 

 

 

Edited June 11, 2018 by uconnjack

[Supreme Pizza]

Kinda hard to tell from the audio file, but is sounds a lot like a bad spot on the flywheel. 

[Supreme Pizza]

 

 

 

[Supreme Pizza]

I usually pull the inspection plate and either turn the motor over with a pry bar against the teeth, or watch the teeth with a flashlight and have someone bump the motor over one little "blip" of the starter a time. Mark a tooth with something, so you know when you have reached a complete revolution. I don't know if this is true or not, but an old school mechanic told me once that the flywheel stops in the same spot 90% of the time, which promotes wear in one particular spot. Doesn't make much sense to me, but I have no particular reason to doubt it.