Got the gearbox overheat message yesterday as mentioned in my other thread, turned the car off, waited a few minutes then turned it on again and drove home, all fine, this morning get into the car, within 1/2 a mile I got the transmission failsafe message, although the transmission was shifting up and down fine, so stopped immediatly, turned the car off, then on again, the message had gone but battery light staying on, drive straight home and park car, put an eletrical tester on the battery, showing 12V not the 14 or so it should be with the car running so think the alternator belt has gone or something?.

So I'm wondering, did the transmisson messgage come up because of the oil getting too hot yesterday and ruining the gearbox oil?, the gearbox seems to fine but this message was displayed then it cleared itself as soon as I turned the car off, I'm hoping a rad change and gearbox oil and filter change will cure it, although should I bite the bullet and get another gearbox even though all gears seem to engage and drive fine I don't want to throw good money after bad.
Secondly what would cause the alternator to suddenly stop working like that?, I can't see where abouts on the car it is to see if the belt has snapped though, although the A/C was still working and usually their on the same belt I think?.

A little off with it at the moment to tell the truth.Hopefully the non charging is due to a belt and not needing one of those expensive water cooled alternators.

Tried removing the fuses for the transmission to reset the transmission ECU, when I put them back in I got, Air Suspension inactive, the DSC and ABS lights were on too, hopefully these will reset themselves.

You need to turn the steering wheel left to right full lock to reset the steering angle sensor if you've been pulling fuses.

You should be careful pulling power as it will damage the nav computer.

Have you checked the terminal connections to the battery and maybe the earth connections? Tested the alternator under heavy electrical load and also with everything off?

Alt's tend not to go ping, but to fail gradually. Low voltage can cause all sorts of problems, so that may indeed have been why you got the gbox inactive message, but perhaps not the gearbox overheat.

For the g/box I would get the fluid/filter changed so that it cools more efficiently in the first instance. The box manufacturer states the fluid change interval is 50 or 60k so if you're overt that then you can expect issues. 

Thanks, did the steering wheel left to right and got rid of air suspension.DSC,ABS etc lights being on.
With the alternator the battery light wasn't on at all, got the gearbox message so stopped, turned the car off, when I turned it back on the battery light was on, getting 11.86 V across the battery with the engine running when it should be about 14.2.
I agree it's more likely a loose connection as it happened instantly, but I can't see if anythings amiss as I can't get under the car as it's on the driveway, everything looks ok from the top though, the AUX belt is still on and driving the alternator.

Sounds unlucky... If the belt has gone, your power steering will stop too and the steering will get very stiff. Water temp guage would hit the roof in about 30 seconds...

I drained the oil twice, first time changing the filter and cleaning the sump, didn't sort the overheat. The only way I solved that was to change the radiator. I also replaced the oil heat exchanger and the hoses but I'm not sure that was necessary..

I'm just going to get it to a garage, Radiator change and gearbox oil change isn't too bad labour wise and I will source the parts myself, my main worry is the alternator, but does seem odd that it would just stop working instantly, however after a google search and some reading it seems this has happened before with other people so I will make sure first, then time to bite the bullet and get the £400 ish alternator.

Just an update, it's awaiting repair at the moment, their going to fit new rad and change gearbox oil, and new alternator, car had enough power in the battery to get down there but I suspect it will need a charge.
The gearbox was absolutely fine today, no warnings coming up and smooth and responsive as its ever been so I hope that the rad change and transmission fluid change will cure it!.
Shame about the alternator though £490 just for the part!, still get the surcharge back on the old one which is something.