Hello Mike,

The transmission itself the 722.6 can withstand upwards of 550+ rwhp (rear wheel horsepower) the drivetrain itself suffers from a 19% to 21% drivetrain loss. The rear differential which is different in both crossfires just as it is in the C320 vs the C32 AMG. The lower one being I believe the 3.27 gear ratio is good for upwards of 400+ rwhp, and the other which should be a 3.08 differential is good for 500+ rwhp. Personally I have yet to see any failure of these diffs, I have a few C32's and 55 AMG's making some considerable rwhp without failures. What is the weak links are the axles themselves, they tend to snap off at the wheel hubs.