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      08-13-2012, 05:03 PM   #79

Drives: 2011 ZCP M3 - 2007 335i crashd
Join Date: Apr 2009
Location: NYC

iTrader: (4)

Originally Posted by talontid View Post
not entirely true. The diff bolts have been discussed at length here before. The problem is the threaded bolts securing the diff shear.
I wouldn't think a burnout to be that bad for the car as the wheels should be spinning. Lateral forces on the car would present more of an issue on the bolts themselves. So standing still, even smoking the tires and giving the driveline and initial shock shouldn't do this.
Maybe if it was at a drag strip going through the box (sticky rubber) or launching the car that I could see, or as said before hard lateral forces on the rear end.Now where is the guy who was designing new bolts??
Originally Posted by talontid View Post
Futhermore, I believe the diff acutally broke after the bolts sheared and it hit the ground. THis is what damaged the heat sink on it too. The issue is not in the diff, but how it's secured.
OP your car looks like a good candidate for the corrosion warranty regardless, it looks terrible under there.
Your posts are rife with misinformation and takes away focus from the real issue. The bolts are not at fault here, rather the rubber mounts that house the bolts which flex. Several performance shops have already developed solid or delrin cased mounts which unitize the diff to the sub-frame and eliminate the flex caused by the diff during hard driving.

So you argue the bolts are at fault? Yet these shops who have spent the time and effort to CNC the uprated diff mounts have not also machined new bolts to go along with their mounts????????? you would think machining bolts that are partially threaded wouldnít be too complicated for them to do right? Yet they havenít. :

The reason they have not and no one else has is there is no need for using partially threaded bolts if you unitize the diff to the rear sub-frame with solid or stiffer mounts than OEM. So fortunately we donít have to wait for someone to machine these in their garage b/c the use of these bolts is moot if you use the solid mounts. Again as with all suspension stiffness uprating there will be some measure of NVH increase.