You aren't going to do any damage up shifting, if you do it everytime there might be extra wear on associated parts. Down shifting if you are good enough you can rev match, but just putting it down a gear you get a nice little shock in your drivetrain that I wouldn't think could be that good if done too often.

 

When downshifting, you don't have to worry as much with rev matching since the Torque Converter will "absorb" any major speed difference between the gearbox and engine.

in fact, trying to rev match when changing gears on an auto tranny will lead to very unpredictable effects since the auto tranny doesn't shift right away (timing will be difficult) and tapping the trottle will lead to immediate acceleration unlike a manual car where the clutch is disengaged so any power goes nowhere (so you end up putting *more* stress on the auto tranny and Torque Converter).

All in all, the only bad thing about manual shifting an auto IMO, is it will make your shifter get looser from the constant movements.

 

try adding a tranny cooler as well. itll help cool down the transmission.

 

you should also get some shockproof gear oil....