automatic runaway in manual mode

[jaxom28]

Navara D40 2010 automatic 4x4
The auto box has a manuel mode where you tap the gear stick to the left and tap down/- to drop a gear and tap up/+ to go up a gear. In 2wd and 4x4 Hi this works text book perfect. BUT in 4x4 Lo in manual mode the gearbox self shifted like it was in D. At the time I was on a steep (25 degree approx) farm track that was loose and chopped up by cattle. I needed 1st gear to maintain a slow steady speed, but the gearbox was having a competition with itself to grab the highest gear in the shortest time. Finally I just rammed the gear stick into the ( - ) until the dashboard gear read out showed 1st, then slammed the brakes on and hit ( - ) (back to first) each time it self shifted. After several (4 or 5) times it stayed in 1st. I then had the same crap in 2nd gear , but only partial success, it would still jump into 3rd occasionally.
I have not had these specific circumstances (gradient and rough surface) before.
On this track it is very slippery when wet so NO BRAKES when DECENDING . The rain arrived before I got out hence my fury at this idiot computer.
I went through the manual and nothing.
I called the local nissan dealer today and was told that this situation had occured before but that it was rare and would enquire for specifics as they didn't know any details.
Has anyone had this happen to them or know of this situation occuring any where ?

[sirLachlan]

Did you start the decent in 1st ? Or bowl on in at 30 kph and try slapping it down ?

If you stopped at the top . Selected manual mode and picked 1st it should have stayed in it if you had little throttle on .

If you bowled on in and tried to slap it down then of course it wouldn't . There are limits programmed into the tiptronic stuff to prevent over rev or wrecking the auto .

[Crash bandicoot]

Tip tronic isn't manual mode. And don't ever assume so. The ecu will always over rule it by default. Which will be to you and your trucks detriment if you think you have control of an auto.

Unless you have personally installed a manualisation kit. There is no true manual mode in a jatco transmission.

[jaxom28]

Started the decent in 1st and the gears self changed up. That time I got away with it as the ground was only greasy. This is the first time it has happened. Would have been different in the wet.
Stopping each time and forcing 1st gear several times seemed to "train" ecu to hold 1st .
Climbing the track was ok (lo2nd) until the chopped up section started , then the ecu played up with the above trouble. Uphill or down didn't make any difference until I stopped each time and forced 1st gear several times seemed to "train" ecu to hold 1st .
On my old navara D21 (import) setting the auto in 1st meant 1st gear only, and in 2nd I had 1st and 2nd gears avalible. I thought that I had similar control in the D40. Nasty shock.
I also called the nissan dealer, and was told that this does happen but is uncommon. However , there is no adjustment/ repair that can be made as there is nothing??? wrong/ out of adjustment.
Strange how the trouble only hit on this track and not other parts of the farm. Prior to this ,using manual mode, I had to tap (+) to upshift a gear, it had never auto upshifted before.