[tonycarreon]

99.9% of my driving is in manual mode. only once i get on the highway and plan to cruise for a while do i then shift over to "D". you will not break anything shifting between M and D while moving. it was designed that way.

if you slow down more than you should for the gear you're in, the car will downshift for you, but it will not downshift for you if you mash the accelerator for overtaking when in manual mode. again, you won't break it by shifting between "M" and "D" while moving. i do it all the time - it's just computers, not actual linkage.

if you're driving along in "M" in 3rd gear @ 70mph and then shift over to "D" you won't break it. it will instead go ahead and upshift to 5th for you. same thing if you're driving along in "D" in 5th gear @ 70mph and move the selector to "M" - it won't break anything because of your change in modes.

"M" is manual mode that lets you have more control. shift when you want. but the computer will still take over if engine damage could occur.

short answer - you won't break it by change selections or shifting gears.