What is this Clip? Strange "Whapping" sound from engine

Hi All, I have recently heard a strange "whapping" sound from the passenger side of the engine compartment. Got out to listen underneath and found this clip on the road below my truck.
Anyone know if this clip is used in our trucks 2nd gen 6cyl? The sound itself seems to be coming from the middle portion of the side of the block. It is not the famous lifter or valve noise. Could it be the serpentine belt? 57,000 miles on the truck.

 

I'm gonna guess the circlip is from something other than your Taco.
Check all parts of your belt.

 

That is a locking washer, keeps nuts from backing out, may or may not be from your truck... As for the noise, it sounds serpentine related. Check your belt and pulleys.

 

That's an E clip not a lock washer may or may not be from your truck.

 

x2

 

Its very shiny and new looking whereas everything in my truck is grimy, so it probably is not from the truck. That said, I will check the serpentine belt.

 

Thats a snap ring used to retain washers and such, We use those on our turbochargers wastegate arm. check anything that actuates. with a cable or lever... but my guess it isnt from your truck.

 

Actually, it looks like the eclip on my trash barrel!
Check your trash barrel.

 

Thanks guys for the info on the clip!

 

Whapping noise on the passenger side? First thing I'd do is loosen the air tube where it screws to the airbox and rotate it counterclockwise a bit before screwing it down.

That dumb tube will make all kinds of racket if it doesn't have tension on it and it's a potential free fix.