[geewhiz]

The brake grinding seems to happen at slower speeds going down hill... that's just one example, I suppose.

Please, can someone offer some ideas?

You say grinding, that is just how it sounds, right? I had that problem with cheap lifetime pads from a discount parts store. IMO, I would hardly believe a dealership used "the best" parts, it seems more likely they used the cheapest parts. Lifetime pads are like rocks and I would guess thats what you now have making the grinding noise. Of course I can't hear it and I could be way off base but thats my "two bits" on it.
Transmission, ???? not clue, sorry! (Yet )