ELECTRIC power to the transmission. Of course the engine would have to be running. Dont ask ME why, because I dont know, its a DOT thing.
E40d's use a band in manual 1st and second AS WELL AS the clutches, in D they do not (thye just use clutches). AODE's engage the OD band in manual second (as well as the clutches).
On my last E40d that I killed it would slip horribly in 2nd gear in D, in manual second it wouldnt, and this is why.