The M differential is actually a variable rate locking differential (0-25% by many diff builder accounts). Its a fine solution and has some benefits but its not to everyone's taste. Many racers actually replace it with a traditional set locking ratio diff. I actually prefer the feel of the older style 25% all the time locking diffs in E36 and E30 because you don't have to wait for them to load up and lock. My E90 M3 often has a split second of time before the diff locks up. That said, either solution is worlds better than an open diff. I'm pretty sure the M performance set up with be a traditional clutch type diff.
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jbrucebmw
BMW CCA LA & GGC
09 M5 | 08 E90 M3 | 95 M3 3.2 | 85 M635CSi | 73 2002tii
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