Transmission Failure
 

I have a 2011 Audi Q7, 4.2 l Diesel Sline 8spd, recently after returning from a holiday the gearbox seltecor was stuck in Park, after turning the car off & On a few times it worked, as I drove off I notived a lack of power.
Now the car sat idle for 2 weeks and showed no problems before hand.
As I drove the car stiuck in 2nd gear with little power and was reving itself, a short while later, the car came to a halt, engine still running but no forward power and smoke billowing from underneath, I stopped the engine put it in park, hoping it would allow me to continue. I had it towed on a flat bed truck to a Mechanic/ workshop which Services BMW/AUDI & Merc's.
They found the error messages point to a power failure to the gearbox computer from the Fuse box.
Once repaired it drove as normal, with a slight loss of power, then 7 days later total gearbox failure warning, jumping out of gears, engine over reving and I had to resort to Manual TipTronic to get forward momentum home.
I managed to get it to a Audi/BMW service agent who has now advised me it needs a total gearbox rebuild costing between $6 -10,000 AUD.
Has anyone experienced this or similar before, as I feel its a Technology failure in the management computers,
Help Please
Craig