engine off danger to trans?

[farmerjohn]

I've got a 3speed auto trans,

tried shutting engine off in Neutral on long downhills, with key in ON postition there is a strange noise as if the engine is still ON but with no power, afraid this is not a good idea...can this damage anything?

with key in off position and coasting downhill the noise and drag are worse

any ideas what happens to auto-trans engines in glide/off?

thanks

john