When you say "while stopping" is it only when the brakes are applied? Or does it ever happen when coasting? Does it feel like it's coming from under the seat to slightly aft of the seat?

Could be this!

I don't mean to scare you, but I had a grinding/moaning sound on my 4runner that I thought were the rear brakes or wheel bearings. Both were fine and I replaced the bearings anyway. This is what it ended up being.

Brian K. Gallus
I have nothing important to say.