Holden Viva Gearbox & Transmission Problems
2008 Holden Viva automatic stalling
It could be a vacuum leak, a split vacuum hose or the like, that's causing the idle mixture to be too lean. It could also be a sensor that's gone on the blink and sending the wrong signals to the computer. You really need to have a mechanic check it for you.
Holden Viva transmission issues
Holden has assured me that there is no problem with the Viva gearbox, so although I can understand you might have lost confidence in the car, I can only suggest at this stage to keep driving it. If you are concerned about the dealer having changed the gearbox then press him to produce the documentation showing that it has been done. It must be there, and there is no reason you shouldn't see it.