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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 04-14-2008, 12:11 AM   #141
kpeng
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Good information Alex, thank you!
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Old 04-14-2008, 08:10 PM   #142
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hey, okay so i have a 02 325i auto, so i can just get a auto 2.5 x3 diff and direct swap it. only change my flanges to the x3 one and thats it. BTW i read the whole thread , all of it. Congrats Kpeng.
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Old 04-14-2008, 08:40 PM   #143
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Thanks n2Bimmer, yes, you shouldn't have an issue.
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Old 05-11-2008, 04:21 PM   #144
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great thread. swapped the whole pumpkin, huh? nice and easy!
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Old 05-11-2008, 06:46 PM   #145
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Great write up man!! Thanks for all the info/help!!
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Old 05-21-2008, 05:43 PM   #146
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Excellent write-up
i just got my 325ci auto swap with the 3.91 from X3
now i'm selling my 3.46
anyone?
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Old 05-21-2008, 06:07 PM   #147
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Excellent write-up
i just got my 325ci auto swap with the 3.91 from X3
now i'm selling my 3.46
anyone?
Do you like it?
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Old 05-23-2008, 02:49 AM   #148
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trying to grasp this diff thing.

from www.bokchoys.com (haha fianlly realized thats what it was...damn vegetables)

anyway...

Final Drive Ratio redline 1st 2nd 3rd 4th 5th 6th
323/325 5spd 3.07 6500 37.2 62.4 94.8 126.9 157.3 -
3.07 7000 40.1 67.2 102.1 136.6 169.4 -
3.15 6500 36.2 60.8 92.4 123.6 153.3 -
3.15 7000 39.0 65.5 99.5 133.1 165.1 -
3.23 6500 35.3 59.3 90.1 120.6 149.5 -
3.23 7000 38.1 63.9 97.0 129.8 161.0
-
3.38 6500 33.8 56.7 86.1 115.2 142.9 -
3.38 7000 36.4 61.1 92.7 124.1 153.9 -
3.46 6500 33.0 55.4 84.1 112.6 139.6 -
3.46 7000 35.5 59.6 90.5 121.2 150.3
-
3.64 6500 31.4 52.7 79.9 108.7 132.7 -
3.64 7000 33.8 56.7 86.1 117.1 142.9


my question is since my 03 325i has a FDR of: 3.46 and and top speed of 139.6 @ 6500rpm

if i gear it up and do diff swap of 3.64 ( hypethically) my top speed would drop to 132.7 @ 6500rpm

and since the site does not show a 3.91, i could only imagine that i will drop even more at top speed? correct?

so would it make more sense to drop to a lower ratio, on a safe and balanced option of FDR: 3.46 to FDR: 3.23

based on the chart from 1st gear to 5th gear speed increases with the lower diff swap. ?

can anyone explain this one to me?

almost forgot...

since it depends on the driving condition

in my case I drive moslty city/ lots of stop and go

from what i found out, that lower gear ratio are recommended for off roading. Now of course im not going that extreme. but from red light to red light obviously i would want some good PICK UP (torque) at the green.
so in my case a slightly lower gearing would make sense?
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Last edited by Autobot325i; 05-23-2008 at 03:02 AM.
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Old 05-23-2008, 03:21 AM   #149
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Yes, if you want quicker acceleration off the line, a diff swap would make sense. You're essentially shifting your powerband.

I think the auto transmissions are geared a little differently too. I have a 3.91 and I'm still capable of 145.
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Old 05-26-2008, 11:30 PM   #150
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What are the exact results? BTW i have a 325i auto.

Faster 0-60? if so how much faster?
Faster 0-100?
Slower Top Speed?
I am cut at 128 anyway so what would that do?
Which would be the best for me?
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Old 05-27-2008, 01:16 AM   #151
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You'll def. have a faster 0-60. I don't know what the top speed is at now, but I can def. still hit 145 in my 330.
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Old 05-27-2008, 02:05 PM   #152
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How much faster? is there any stats? enough to justify $400
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Old 05-27-2008, 02:06 PM   #153
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How much faster? is there any stats? enough to justify $400
No real stats. I assure you it's noticeable and well worth the $400.

Put it this way, before my diff swap, my car ran a 15.45 quarter mile. After the diff, it ran a 14.9
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Old 05-27-2008, 02:27 PM   #154
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and you ordered from that car part store?
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Old 05-27-2008, 02:32 PM   #155
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Yes. It's not a store, they search junkyards around the country for the part you want. You can then look for the deal you want.
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Old 05-27-2008, 03:13 PM   #156
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what do i do if i dont want to give out my credit card number, should i get a pre paid card.???
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Old 05-27-2008, 03:27 PM   #157
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what do i do if i dont want to give out my credit card number, should i get a pre paid card.???
I don't know. Why wouldn't you want to?
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Old 05-27-2008, 03:32 PM   #158
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I don't know. Why wouldn't you want to?
because i dont fell confortable giving out my credit card number to a junk yard.
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Old 05-27-2008, 03:37 PM   #159
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That's stupid. They're a business just like any other. A lot of people have done the same, and no one has had an issue.
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Old 05-27-2008, 03:40 PM   #160
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Did you just keep searching that site till a good deal came up because the only one on there right now is $450.
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