i'd avoid down shifting newer cars, the trans aren't made for that, as a cdl driver the rule of thumb is to lightly hit the brake and slow down 10 mph, let off and roll till you hit the speed limit, and repeat as needed to avoid over heating the brakes, and in a big truck the brakes will heat up real fast and just stop working altogether and thats no damn good. I've applied this to all cars i drive and have have no warping or brake fade at all.
cant help with the trans problem, im sure someone with trans know how will chime in.
