minor squeak/creak sound from rear

[Cool_V_300C]

OK, I can reproduce it now by backing out of my driveway. There is
a small dip at the end and it's when the suspension compress/decompress.
Kind of like an old mattress spring, like "crik-eeet".

It is very faint and can't be heard outside of the car, but it can
be heard from the inside.

any ideas what to check first? I want to upgrade my shocks/springs
with Pedders, but I'd like to find out what could be making the noise.

I don't have any suspension mods in the rear. I do have the bump
steer and radius rod bushing from pedders in the front.