Of course the E90 335i doesn’t come with a limited-slip differential, because that would be sacrilegious to BMW’s M department. Although, that’s what they’ve been doing since the E36 era – only M models had the privilege. For the usual driver, it doesn’t mean much, but to someone who’s trying to autocross or do other track-related activities, it leads to some severe one-tire-fire. BMW thought applying the brakes in a creative way would suffice for the no-LSD option, and it definitely does for a lot of people, but it’s nowhere near having a mechanical LSD like it should. If you’re one of the lucky few before BMW welded the ring gear, you can buy one and drop it right in. If not, you’re stuck with machining the ring gear off doing further machine work to turn it into a bolted setup, or buying the entire differential pumpkin and swapping it out.