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Rear diff question... testing the waters...

2286 Views 36 Replies 13 Participants Last post by  PropellerHead
What kind of acceleration gains could I get by modding my rear diff? What if I put in a 3.73 or a 4.10? How much would this cost me?

I just got talked into test driving an '06 beautiful black/black M3 (with the competition package, too) at crevier BMW and I want it. :( Obviously, I can't afford a 62K car as a 21 year old student (although the salesperson swore I could :tsk: ) but I was wondering if I could get that "seat of the pants" feeling of shear acceleration out of my 540i with a new diff...?

Also, I don't really care about fuel economy or top end (I chicken out over 140ish anyhow) so, is a 3.73 or 4.10 LSD (or even open) right for me? Where could I get one? Thoughts people, thanks! :)
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The M5 dif is not a direct swap. You need to replace the half shafts along with the dif. Dave Zeckhausen did this and posted about it on Road fly a couple of years ago. Its a lot of work.

I too am thinking about this and I've talked to Koala motorsports a couple of times. The owner -- Brett Anderson I think it is -- does difs for lots of BMW racing cars and writes for the tech column for the BMW CCA magazine Roundel. He's also very patient with stupid questions. I'm planning to buy from him when I get the coin scraped together.
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