A mate's T5.1 DSG has recently had the O/S splines fail, as in totally stripped and no drive. This is when I discovered the DSG has a completely different set up to the manual, where the gearbox has the female splines, and the driveshaft has the male splines, there is no intermediate stub shaft.
Now this failure is also happening on the offside of DSG boxes, I think we can rule out soft metal, as the near sides virtually never fail. The common denominator is the fixed transfer shaft. I think that because there is no CV joint on the O/S of the gearbox, there is nothing to allow for the driveshaft to flex, so any mismatch of alignment and wobble allows the splines to move around and wear out. As soon as the wear is significant, the grease disappears, water gets in and the process accelerates until failing. I'm sure if they'd fitted a third CV joint to the gearbox end, O/S driveshaft failures would have been rare, and no different to the N/S.
My mate was told by VW that no parts are available for the DSG apart from clutch packs, so a new box was needed. He went to an auto box specialist, who sourced the planet gear with the splines that lives inside the diff and rebuilt the box. (I gather the DSG's are made by Borg Warner, so they probably source parts directly).
Anyway, all back on the road and working fine.
I think I'll check my T6.1 drive shaft at the 80,000 DSG oil change, and wallop some more grease in.
