[ajsalida]

I think the short answer is the AWD on e9x cars benefits from 2 things: one it was designed for 335 power levels and beyond. And then by the time it came out BMW had already gotten good at X3 and X5 systems.

If you recall there was no e36 based AWD system, and so only the very limited production 325ix e30 AWD car prior to e46 coming out. One might say the e46 is where BMW cut its teeth learning, and under pressure partly due to the rising popularity of Audi, VW, Subaru and others already established there. In typical fashion at least on the e9x cars they appear to have overbuilt it, and WAY over built it for 328 power levels. In some sense sort of the way they way overbuilt the N54 internals, where people are now getting 800+ WHP out of them with dead stock motors otherwise. In that case the N54 was BMW's first volume turbo gas motor, so they made sure they nailed it, and nail it they did.

The only thing I wish they had done with AWD is a more flexible TC, like that could be locked or set by driver, and a true rear LSD. You can add a rear LSD fairly easy but the TC we are stuck with. Still for as relatively simple as the system is, it is very robust and performs well. And frankly not many TC's are breaking even on tuned cars so really no pressure for anyone aftermarket to develop an upgrade.