When my partner is driving my automatic Nissan Murano he keeps changing down from drive to neutral while going down slopes. I tell him that this is harmful to the gearbox, please prove me right!,!
You are right, coasting down a hill in neutral can severely damage the internals of the tranny due to a lack of proper lubrication due to an idling engine and the high speed of the transmissions internal drums and clutches that are still spinning cause your coasting. Back in the old days when automatics had rear pumps also this was not a problem but with new stuff you just can't do that and expect a transmission to last. Now in most states it is a traffic infraction to be coasting out of gear in any vehicle, so not only is he damaging the transmission he i also asking for a ticket.
Thanks for the points