I have a 2004 Chrysler Sebring and a 2006 Touota Sienna. Am I asking for transmission problems by down-shifting to assist in slowing down at exit ramps and down steep declines?
Use your brakes in conjunction with the transmission to perform these tasks. If you are thinking you are “saving the brakes”, remember an auto tranny repair runs $1000-$5000 while brake replacement averages $250/axle.
It is extra wear on the transmission that cost a lot more than the brakes. While I use a manual transmission, I seldom downshift for exit ramps or lights. brakes work well and are cheaper, in addition with automatic transmissions, if a situation comes up where you need to shift quickly, you will need to think about shifting as well as other things. Generally it is best to stay in drive.
Now about those steep declines: There you should be down-shifting. Under those conditions the brakes can overheat and fail, so continue to use your transmission to help control your speed on a steep decline.