My A6 gave out in Vegas. There was a sound like a manual popping out of gear and I lost everything. No park, reverse or any forward gears. I push the accelerator and the speedometer will register but the car is stationary. After a bit I went back to the car and it went into gear but quickly popped out again (within 30 seconds of being in gear.) HELP!!! is this a torque converter, or a T-case or something other than a transmission rebuild?