Originally Posted by Squidz
^^ I have to agree with several others above. Don't downshift to slow down, only downshift to go faster. Brakes are on the car for a reason, and they are indeed..._much_ cheaper than trannies and clutches.
do you move the gear selector to different gears when the clutch is in and you are slowing down?
if you do, you are putting more wear on your synchros.
downshifting (and rev matching) won't have any more of a negative effect on your drive train than any thing else.
to save the synchros you should double-clutch, I'm sure others have chimed in on this, but anyway, I've driven a couple of cars over 100k miles downshifting with rev matching, but no double clutching, no synchro issues, and on my old integra I put almost 200k on it without seeing any noticable wear on the synchros.
anyway, know that there are potential issues not only with doing a downshift incorrectly, but that there are potential issues with wearing out the synchros faster.