Noise Coming from rear when in Reverse

Hi, my friend has a 2001 Toyota Tundra V8 4wd, and when he accelerates hard in reverse, a loud squeking noise happens. We changed the rear brakes, thinking that was the problem, but now think its the u-jounts or something. I would appreciate it, if anyone could tell me what is making this noise.

I had a similar noise:squealing when in reverse (even coasting). I cleaned out the drums and it eventually went away. Hopefully his is that easy.

EDIT: my sound wasn't constant. there was one squeal for every wheel rotation or so