what specie is saying is correct to a certain extent. however i would argue that stopping quickly in any manner wears on your brake pads or transmission depending on how you are slowing the car down. fortunately for all of us honda transmissions are very reliable and hold up really well. ive had 3 different crxs with over 150k miles and their transmissions were all fine. im not saying you should downshift from 5th to 3rd everytime you are coming up on a stop light but saying within moderation downshifting isnt going to damage the tranny.