When I back up and turn I get this AWFUL noise from the back wheels. I have no idea what it is. Has anyone experiencd anything similar?

 

Did you find the source? I am pretty sure I am having the same noise from the back wheels only when backing up.

 

Have you checked the wheel bearings? If the wheel is lifted off the ground, see if you can grab the wheel at 6 and 12 and try to see if the wheel has play in it. If so, you likely need to replace the bearing / hub.

 

I vote seized caliper.

 

I second seized caliper.
Apparently it's an issue on these cars, and I'm in the process of replacing brakes on all four corners because of the wear on the rear right caliper.
Check it out before it becomes a bigger issue. Try to get a look at the caliper and see if the pad is pressed against the rotor. If left like that it'll wear down the brake pad and be metal-on-metal.

 

To the OP - have you done any investigation or diagnosis? Have someone pump the brakes and have a look what's going on. Noises are visual.

I also vote seized caliper, but more specifically, I vote seized slide pin (or pins) in the torque member. If you can get them out (might need a vice), thin them up a hair with a bench grinder and re-lube. They should be find to reuse as long as the caliper piston (and boot) still looks good. No need to replace the entire caliper for this (and most re-man'd calipers don't include a new torque member anyway).

 

A body in the trunk?