BMW Canada contacted me, took down additional information and never called me back. I got irritated over this past weekend so I decided to tear down the rear of the car. The diff is 100% in good shape, the aluminum on the back of the diff broke. When that happened the yoke of the driveshaft broke and the subframe got dinged. I ordered all the parts today and will install them over the weekend, I will be sueing BMW Canada for time lost and parts/labour.
tibra1 you seem like a fairly knowledgable guy, the fact the rear casing broke off the car is ludacris. I have been working on cars for 15 years++, as a mechanic, an engineer, and as a enthusiast. I have never, not once (minus the e36 m3, thats a different story) seen a diff fall off a car. I've seen transmissions split, subframes twist, transmission crossmembers break, you name it I've seen it. A diff should never fall off a car, stock street car or not. You should be able to break axles, driveshafts, burn ring gears/spurs before a diff falls off a car. A burnout essentially should never break anything since theres no real load, on the other hand wheelhop can break many things but not a diff housing. The m3 rear housing is the weidest most unintelligent design I've ever witnessed on a car (many bmw's are like this, I'm guessing to eliminate NVH but from a durability/reliability standpoint the design is faulty). The bolts are also in shear which is a terrible design, should be in tension since a bolt is strong that way, why is there only 1 bolt on top? Anything that requires any real strength will have the bolts in tension/compression, its design/engineering 101. Also aluminum fails without a doubt, putting 1 bolt and no re-enforcement will cause it to break. Since aluminum fails (fatigue limit) Aluminum wings on airplanes are constantly x-rayed and tested for cracks. You can deisgn aluminum in ways that it never sees extreme loads but obviously that didn't happen with the e92 m3. Solid bushings will help alleviate some of the fatigue, a brace seems like the best option.