had recently rear sub frame crack fixed by RAVEN
 

i bought my m3 almost 3 years ago and guy told me there was sub frame re-inforsment kit installed(my mechanic confirmed, but ewrething was coverd with rast proof so hi cant see quality of welds). so i was never looking there for any cracks. one day at cayuga track i heard some metal noise and start looking and found some big cracks!!!! mechanic who installed re-inforsment kit didnt do a good weld an it become a disaster. at some point i was ready to sell my car. my mechanic told me hi cant handle this repair an i have to find someone who have lots of expirience with this chassis. i found RAVEN/BAVARIAN Motors. one i got to the shop i was very impressed how many racing bmw was in the shop. repairs all done and im very happy, here is some pix

some pix afrer rust proof removed
 

previos fix with very poor weld

repair
 

so after previos repair regular reinforsment kit wont do the job, so they have to desigh they own kit with lots of plates

tower brace
 

its not my daily draiver, most of the milage car get on the way to the track and on the track, so they weld me in tower brace, they connect sub frame to the body, after this brace car more stiffer!!! Good luck with your M, and hope u dont have to go thru the same repair!!! if u gettting kit installed make shure its done frome first time, cuz to fix somebodys mess is a mess hehe*wave*

What was the total cost?

3000+

Money well spent.

If I ever pick up an M3, this will be my first mod before FI :D

If u do this before problem starts I'm pretty shure it will be cheaper than to fix after somebodys mess

Why do they crack ?
Too much power or poor choice of metal used in building the car?

There was recall but it's over, not all of the e46 cars have it

*th-up**th-up* for Steve at Raven. He's an outstanding fabricator. I'm also very pleased with all the custom metal work on my E12 especially the exhaust system.

I'm very happy with his work, everything looks very clean and solid. Hehe

What are the symptoms of a damaged subframe?

Cracking noise and after I chech in trunk and seen cracks

Power has nothing to do with it. 323s been reporting failures as early as 50k kms.

Its a mystery, well not really but much so. First , the design of the rear subfloor hasnt changed much from the E36 which had a bad bad design to start with. And then its the sheet metal suppliers at certain years. 98-02 have THE most damage , 03+ cars rarely are seen with damage because BMW physically changed the rear subfloor design after 03. M3 will all have damage because they havent got the new updated subfloor as standard.
Cracks in the rear subfloor sheet metal. Those are the symptoms.


Poor maintenance also leads to this. Reaplce your diff bushes, subframe bushes and in general keep your car in good shape if you wish to enjoy it.