check your rear leaf spring shackle busings /inserts spary some wd40 or silicone lubricant on them .

 

I have this as well, but marked it up to my grill being broken on the inside and plastic rubbing. I do not know if it is the same sound for you but I just go move my grill and can re-create the sound.

 

I have an '00 4runner that also makes a very noticable "chirp" that almost sounds like two pieces of metal hitting eachother, or like a a metal chain hitting soemthing(?) I'm not positive what it is but ive narrowed it down to the front driver's suspension/steering components. i mostly notice it when hitting pot holes or bumps in the road. the suspension on my ride is shot to hell so i figured it might be the the shock(?) or just something that rattles a little bit as the wheel "floats" over bumps since the shock is blown out. my vehicle has 199k on it and drives/steers fine so i think its a harmless noise.