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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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2000 BMW E46 323i
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279 Posts
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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2000 BMW E46 323i
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279 Posts
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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