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Go Back   E46Fanatics > Tuning & Tech > Driveline, Engine & DME Tuning

Driveline, Engine & DME Tuning
Talk about driveline improvements, NA tuning and DME tuning your E46 BMW here. This includes diffs, intakes, exhausts, chips, software and OBD tuning.

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Old 02-28-2012, 05:48 PM   #1
matabamatt
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Best gear ratio?

2003 325i 5speed step right now wondering what would be better ratio
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Old 02-28-2012, 05:57 PM   #2
JJR4884
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Originally Posted by matabamatt View Post
2003 325i 5speed step right now wondering what would be better ratio

Honestly dude just search.... ton of threads on diffs. I think for your car you have a 3.07 or a 3.23, not sure..... those are high enough, I wouldn't suggest anything higher like a 3.38 or 3.46 unless you have a 6 speed.

However that's your preference, some people don't mind cruising at 4000 rpms on the highway.... hell no for me.


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Old 02-28-2012, 06:17 PM   #3
KickTheCAN
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5speed steptronic?

Go 3.91 then.
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Old 02-28-2012, 09:21 PM   #4
Steven747
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3.46 diff in mine and at 80 I'm at 3200 rpm
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Old 02-29-2012, 05:10 AM   #5
matabamatt
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5speed steptronic?

Go 3.91 then.
would this make my car a lttle quicker but still be good at highway speeds say about 80mph
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Old 02-29-2012, 08:50 AM   #6
Drewfus2101
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Search.

First, you need to figure out what the options were for your car. It should be obvious as to what ratio is in your car.

Then you can use an online calculator to show what the RPM change will be if you want to change to something like a 3.91.

My '03 330i auto came with 3.38 rear end ratio. I wouldn't want to go up more than 0.30 or 0.40. Last time I used a calculator, that changed the RPMs at 70 up by about 400 or 500.
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Old 02-29-2012, 08:54 AM   #7
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Real OEM say for a '03 325i you've got a 3.46 ratio. I don't know that I'd go any higher. If you can find something in the 3.6X range, it might be worth it, but past that you just have the 3.9X range, and thats a pretty good jump.
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Old 02-29-2012, 09:26 AM   #8
KickTheCAN
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would this make my car a lttle quicker but still be good at highway speeds say about 80mph
http://forum.e46fanatics.com/showthr...965&highlight=
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Old 03-01-2012, 05:16 AM   #9
matabamatt
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Real OEM say for a '03 325i you've got a 3.46 ratio. I don't know that I'd go any higher. If you can find something in the 3.6X range, it might be worth it, but past that you just have the 3.9X range, and thats a pretty good jump.
just by .30 higher can jump the rpm that high? i guess it wouldnt be that worth it unless the price was good
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Old 03-01-2012, 05:19 AM   #10
matabamatt
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thanks for the link... you did the clutch fan swap to electric?? was it hard
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Old 03-02-2012, 01:33 AM   #11
diablorojo
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I put a 4.10 in my steptronic (before the conversion) it was loud cruising but I have header, exhaust, SC, etc...prob not so bad with no SC. I still have that gear in 6 speed and it still is loud...but the acceleration was ridiculous in my auto setup....
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Old 03-02-2012, 01:39 AM   #12
KickTheCAN
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thanks for the link... you did the clutch fan swap to electric?? was it hard
Not at all. I did it while I was swapping out the cooling system so the original fan had to come off anyways. The new electric fan is drag and drop. Just have to transfer an item from the old fan on the new one and plug it into the power source.

This, however, will render your pusher fan useless- the fan that's right in front of the radiator that sits right behind the front bumper. I havent removed that yet, but you should as it blocks airflow.

Makes the car real quiet and it works...made a four hour trip in hot weather the other day
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Old 03-02-2012, 03:39 AM   #13
ICONIKE46
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3.46 is the highest I'd go in a 325 5 spd. Anything higher than that and you'll be cruising at pretty high rpms.
3.63 is also doable but again the rpms are just going to keep going up while cruising.

Next time, please search. There are PLENTY of threads and plenty of info on the forums regarding gearing. gl with the project
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