Someone correct me if i'm wrong, but I thought the 335d only comes with auto because the manual couldn't handle the torque.
That is correct sir.
According to this page
the auto gearbox code for the e92 335i is GA6HP19Z. Curiously, on ZF's website
, the lowest code I can find on a gearbox is 6HP21Z and it can hold 450NM of torque
Edit: the third page on this pdf
(very informative btw) shows the 6HP19Z is rated for 400NM of torque on the input shaft (times .737 for the conversion and you're looking at 298lb/ft). I'd imagine that's the continuous rating so multiply by 1.5x for instantaneous loads and you're probably looking at 450lb/ft as the upper limit for what our auto tranny's can handle.