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Differential Upgrade

1603 Views 18 Replies 14 Participants Last post by  Lotek
I am considering a diff upgrade to a 3.23. I currently have a 2.93 final drive on my new 330i (6 speed manual tranny). For anyone who has upgraded their 330i final drive, I notice that Dinan offers 3.15. They content that higher ratio's may cause problems with DSC and/or ADB. There is a concern that traction control will get confused with shorter final drive. Anyone have problems with on board computer or DSC associates with differential upgrades?
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IIRC, the 6 speed has a shorter first gear already and since you have the 2.93 now you'll probably want to stick with a 3.15.
You can swap out any E46 rear you like so getting a 3.15 or 3.23 is simply a matter of either finding a used one from someone who's already done a swap (or from a wreck) or buying a new one from a BMW dealer that discounts (Circle, Hendrick, Pacific), cost about 1K. Don't get the Dinan please, it's just BMW stuff with Dinan surcharge. :thumbdwn:
Brett has been approached in the past about this issue and he was very helpful in discussions with me about doing a Quaife LS but we could never get enough people to get an E46 unit in production.
I think he'll tell you basically what I told you above since he can't get the gears to do rework on the internals.

My plan: I already have a 3.07 and hope to pick up the 6 speed one day for that shorter first gear and the overdrive.
Add schrick cams and current modifications and I'll be a happy guy. :thumbup:

Edit: just looked it up - the 6 speed has a 4.35 first gear as opposed to the 4.21 in the 5 speed so my opinion, try out a 3.15 but I don't think the 3.23 will make you unhappy.
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AlexRDI330ci said:
Roose - Like the sig quote.
Here's one from www.protestwarrior.com (check it out - very funny story about the SF rally):

"War is an ugly thing but not the ugliest of things; the decayed and degraded state of moral and patriotic feelings which thinks that nothing is worth war is much worse. A man who has nothing for which he is willing to fight, nothing which is more important than his own personal safety, is a miserable creature and has no chance of being free unless made and kept so by the exertions of better men than himself."

-- John Stuart Mill

PS - I'd like a lsd, but it soes seem unlikely. There's a lot of fans, but getting people on the field is tough.
Great quote. I have it on my wall at work.
Thanks for the link, that's some great stuff. Hope they don't mind if I steal one of the signs.
To keep this on topic, answer for isaacly- yes, the higher the number the better for acceleration, kind of a "torque multiplication" but you will cruise at higher rpms. Think of the gearing on your 10 speed bike, which gears are easier to take off with and which ones give you more torque? Same ideas and you look for the best combo for take off and cruising.

Also, I've given up on the LSD idea (part for diff, not drug). Doesn't seem we'll get the Quaife and I've seen negative feedback on the HIOP. I would like to hear more from HIOP owners though before completely dismissing it.


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Nick325xiT 5spd said:
According to my math... 2.93/.83, a 330i with a 6spd will run LOWER revs with a 3.46 diff than a 330i 5spd with a 2.93.

My autox tires give me an effective gearing of 3.43, which is just plain wonderful. Get yourself a 3.46. No need for half measures. :D
Hmm... lessee
The overdrive is .85 according to BMW web site.
2.93 * .85 = 2.5 overall ratio for 6 speed.
2.93 * 1.0 = 2.93 overall for the 5 speed
3.15 * .85 = 2.68
3.46 * .85 = 2.94
So yes, 3.46 will let him cruise like the 5 speed, but why?? I want that nice cruising while still getting some extra kick in first. ;)

5 speed first gear:
4.21 * 2.93 = 12.34
4.21 * 3.15 = 13.26
4.21 * 3.46 = 14.57
6 speed first gear:
4.35 * 2.93 = 12.75
4.35 * 3.15 = 13.70
4.35 * 3.46 = 15.05 Wow! Shift at redline - 1st= 32mph, 2nd=55mph
As we can see, this choices are subjective and each user should do their own calculations before deciding. :)
Everyone should play with Todd's nice little calculator, here it is:

You bring up an important point - one must take into account any tire/wheel changes from stock.

Uh oh, boss is giving me dirty looks. :)
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