I don't think it'll harm the transmission. I did that myself quite often when I had the auto in my 2.6.

__________________
1990 190e 2.6 - The only one I can really call "My Car".

1987 190e 2.3 - The donor car's up and running, only mods are Euros and a Sony headunit. My Dad's runabout now.

1990 300e 2.6 - The parents' ride.