Auto box shifts up a gear...

Hi everybody- I'm wondering what the parameters are for the auto to shift up a gear when coasting down a hill? I drive down a long hill every morning at 60-80 kmh to work and sometimes when I dab on the brakes, it'll shift from 4th to 3rd, thus increasing engine braking. But it doesn't always do it and I haven't noticed it doing so at other times! The engine hasn't warmed up completely so I thought that could have a bearing on it, but that seems odd. Anybody have any ideas, or thoughts? I'm not fussed unless this is not a feature but a fault.
Thanks - Roger

It's part of the engine braking. If the D40 is in overdrive and you hold the brake for a certain amount of time to maintain speed, the ECU will instruct the Transmission Control Module (TCM) in the gearbox to knock back a peg or two. Mine usually drops from 5th to 3rd.

If you flick the overdrive button it should pop back into 4th.

Mine holds revs and speed but like Tony says it's only if you hold the brake for a certain time (a few seconds is all it takes). It can be a little annoying especially on hills like those coming into Perth or Adelaide because at times you might need to give the vehicle a little gas half way down to move around a slow vehicle or even where the hill may flatten out for a hundred meters or so. But I've only found it annoying because I believe the amount of pressure needed on the accelerator to get it driving is too much, although I am picky about my economy so feeding excess juice into it is not natural to me

Last time I drove a D40 I noticed this.

Its a good feature. Xtrail's do it to.