Factory Five/superformance/backdraft

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Wanab5150,

You are still confusing me on the "rear end" question. A Ford 9" is very heavy and heavy duty. They were often used in trucks. I think that is one of the reasons it stands up to much abuse. But it was designed many years ago when the easy way to make something last was to make it big and heavy.

Along comes BMW back in the 80s with a very stoutly designed differential that is quite small and light in comparison. They put millions of them on the E36 series cars and many of them were raced in stock form with virutally no problems. 400+ horsepower? Not too often. But when Backdraft put one in their Cobra replica, it really got a workout! They built more than one car with much more than 400HP and as I understand it, no problems. They even drag raced one of the cars! Talk about abuse. So, perhaps newer technology can be both better and lighter. You can also have one built even "beefier" for road and drag racing. I thought about having this done to my stock differential, but can't justify the approximate $2K upgrade charge. If I was racing it, perhaps, but for just blasting down the highway, I feel my stock unit is just fine.

Did you ever have problems with any of your BMW differentials? (I know they are not all the same units) Just curious. I understand the dealerships repair vitually none of them, unless they are really old. Good old time German engineering, at least in this area!

The race car mantra is "lighter is always better", as long as it works! And the BMW units seem to work very well under many conditions.

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