I remember when i was in Dominican Republic i was driving n this longggg down hill and i had to down shift because they brakes might fail or overheat or anything bad could happen because the road was so long. auto or manual everyone in that highway knows to go down slow, so many ppl have die there that they have the virgin mary statue on a curve. is a mountain but the road is straigh down for miles and at the end is nothing but curve really bad. but like everyone said "Leave it in D4 for the climb"