Hi,

I have a TL '06 and my question is it smart to switch from auto to manual while driving at 40 mph. Would it damage the transmission. I want to use manual when going through mountains when there are tons of ups and downs. Or is it best to pull over and change it to manual instead of changing it while running?

 

It is design to be used when you want to use it. From a start or when driving it.

 

it wouldn't let you shift into manual if it would harm your transmission.

 

You can also drop it into L if you feel the need to. I sometimes use this to slow down if I see a cop coming from behind and don't want to step on the brakes.

Moving it into manual will still retain the same gear you were in, so it didn't really do anything except change the indicator on the instrument panel. The change will come when you shift.

As said above, it won't let you do anything that will harm it, which is meant for the occasional lapse in judgement, not as a general rule.