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Discussion Starter · #1 ·
Hi all!

I have just acquired my e46 323i manual convertible and starting my drift build, so far I have found so much useful info here and was hoping to get some specific help on the diff.

so, if I’m right I have a 3.07 ratio medium case (188) diff? I want to get a shorter ratio to get more torque to the rear as I believe the weight of the Vert makes it a little harder to initiate a slide, looking to get a 3.38 or 3.46 but struggling to figure what diffs actually fit. Have an option of a 330i auto (3.38) but apparently the prop shaft won’t fit due to bolt pattern?

Searched the site and google but can’t make heads or tails of all the info, hoping I can get some clear advice of exactly what I need, thanks in advance to anyone who contributes to easing my headache!
 

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2005 330ci
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I recently bought a 3.46 diff to replace my 2.93(?). The 3.46 has a 4 bolt range and I’ve read I can swap/install my 6 bolt input flange. Hope to install it this week.

Maybe you can do the same?

Edit: I have not found anywhere that sells individual imput flanges.
 

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2000 BMW E46 323i
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I have a 323i but saloon. I also changed my stock 3.07 to 3.38. A almost direct fit is a diff from 320i M54 (2.2L) equipped cars with manual transmission. Only thing you have to do is to install your 3.07diff output flanges, because those cars have 188 diff but they have 4cyl (small) halfshafts, thus also small flanges. Input flange is 4bolt direct fit on your stock driveshaft. If you want 3.46 diff a 323i or 325i touring manual 5 speed gearbox cars have them. Then you don´t have to replace flanges at all.
 

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Discussion Starter · #4 ·
Ahhh, so does that mean all the 3.46 diffs will be a direct fit to mine as it has the 4 bolt flange, but all 3.38s would require the flange to be changed? Or is it more specific that that? I hear the input flange job isn’t a good one and has a good chance of issues arising if not done perfectly?
 

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2000 BMW E46 323i
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Well, no...the 320i 125kW M54 2.2L engine equipped E46s with manual transmission as i stated above have a 3.38 diff that will fit your driveshaft so no INPUT flange swap needed (and that´s the best thing), just swap it´s OUTPUT flanges for your original 3.07 OUTPUT flanges and you are good to go. This is exactly what i did to my car so i know it works. But beware of 320i E46s with older 110kW M52TU engine, those utilize small case (4cylinder) diffs but with the same ratios (3.46 for example) so it´s easy to make a mistake when searching for a medium case 3.38 diff. And yes, 3.46 with 4bolt input flange from 323i/325i Tourings are direct fit with no modification whatsoever. But i know that 323i or 325i E46s with auto transmission came also with 3.46 diffs so i think that this would also be a direct fit. If you are not familiar with diff jobs i suggest to stay away from swapping input flanges. You see guys here buying 3.38 diffs and swapping flanges becaause they buy diffs that came from cars with 6speed manual transmission, so they utilized a CV-joint instead of U-joint on the driveshaft-diff connection. But are you sure your 323ci (convertible) has 3.07 diff? I thought that they came with 3.46 from the factory even with stick shift.
 

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Discussion Starter · #6 ·
I will need to get under it and see if I can see a sticker, I could be wrong but from why I have read it’s a 3.07, are they different in the US to EU? Just so much info out there it’s hard to figure out. I used this for some guidance but still wasn’t sure 2000 323ci differential swap
 

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2000 BMW E46 323i
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People often refer to the convertible as coupe. 330ci was a badge used for coupe but also for convertible so i think that´s why there is confusion regarding diff ratios. As far as i know the convertible 323ci should have 3.46 diff due to additional weight, the same principle as touring. But i can be wrong. What RPM is your engine at at 100 km/h in 5th gear?
EDIT: I just checked realoem for 323ci convertible diff ratios. It says 3,23 for manual and 3.38 or 3.46 for auto gerabox. Now this is what i call confusion lol...the best would be to determine your real final drive ratio using either RPMs at given speed or just check your label as you said above. It also gives different final gear ratios on US vs EU so sorry if it´s somehow confusing. I stand corrected.
 
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