Mystery sound coming from the rear of my 3rd gen taco

Hey everyone,
i have a 2016 Tacoma SR5 2WD with 110k miles on it. Over the past year i have been hearing a mysterious squeaking sound coming from the rear area underneath the bed. The sound would happen once in a blue moon but lately i have been hearing it every time i drive my taco. It seems to only create the sound when the truck has "warmed up" and only on take off if i am at a complete stop. Some say that it is the u-joint but some say otherwise so i was hoping to bring this up hear to shed some light on my problem. I uploaded a video as well in hopes that it would help.

thanks!

 

Might be backing plate rubbing on the rotor. Have you checked to see if there is any play in the drive line