@Devilz Walton Audi know at least one DSG gearbox inside out.... mine!
Dig through the chat history: mine is on the same STronic box as the low/mid end TDI's and it failed almost exactly 3 years ago - no oil change history required: it was at <8000miles, 3yrs and 3 days old... and that's on a supercharged TFSI PRE-remap*, so NOT a lot of torque compared to oil-burners - only slightly more than a 2.5TDI/2.7TDI, similar to the lower end 3.0TDI. My A6 has a full Audi Service History and was completely stock at the time of failure.
*Even after the remap the torque wouldn't have been a problem for mine - the TFSI's are very different beasts to remap compared to TDIs - you don't touch the low RPM torque and peak torque (much!) - it just doesn't bleed supercharger boost pressure prematurely and holds most of that 440Nm to 7000rpm now
....
When it failed: as soon as the DSG tried to shift up to 2nd, it disabled that half of the gearbox and it just disabled gears 2,4,6,R. I had to drive it in "Sport", to get it to rev out so it didn't bog down on each upshift as it was going 1-3-5-7.... AND I had to turn the car off and restart to get into reverse, three point turns were a PAIN. Text book Mechatronic failure.
Turns out that there's a known problem with the S-Tronics up to about 2015: all related to why Audi did a full safety recall on the S5's and S4's in North America** and why they only put the STronic in the 204PS V6 TDI, never the 240-270-ish PS TDI's until that issue was resolved - there is a re-designed mechatronic unit on the later models (and on all recalled cars) - apparently should be good for a LOT more torque, but I'm not sure how much - if you were considering remapping a TDI - torque isn't an issue for my remap
**not clear why they didn't actual recall elsewhere, but there were a couple of reports in the US of S5's completely seizing up in the middle of highways! (cue Fight Club-style conversation about publicity/compensation, etc)....
And in reference to the BiTDI's - they've always been on the ZF 8-speed and probably always will as they can handle a LOT of torque - pretty sure that's the same drivetrain that's used in the 4.2TDI in the A8/Q7.