The DL501 is an amazingly strong gearbox. Doesn’t mean there aren’t bad ones but the actual gear set is stronger than what you find in the Graziano gearbox in the R8.
The weak link is the clutch basket it appears. Some will break off the “fingers” or teeth and you’ll find these when changing your ATF side fluid. They can cause an imbalance which leads to other issues (naturally). The 3.0T guys with the DL501 seem to suffer the most from this (with stock flywheels/clutches) but there are also 10X the number of S cars vs. the RS5 so greater numbers means greater number of failures. I’ll see if I can find Jerry’s photos of his clutch basket teeth that were found in the ATF pan.
There are a few others who bought the flywheel early on and are not having issues and have 10’s of thousands of miles on the flywheel. They drive their cars hard too. At least one has chatter and uses the “chatter” tune. But his flywheel is still going strong and he takes his car out on slow group drives all the time (slow being sarcasm).
Out of all the failures I know of, none have been cut and dry, there have been extenuating circumstances so it makes it very hard to determine where the issue is starting. I personally would not have a problem installing the flywheel, along with the new clutch, in my own car.
The center section of the flywheel can’t be as hard as the input shaft for obvious reasons.
