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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > NA Engine (non-turbo) / Drivetrain / Exhaust Modifications > 328i diff upgrade?



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      07-30-2022, 05:11 AM   #1
E90jacob
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328i diff upgrade?

I'm looking to upgrade my differential on my e90 328i AT.
Does anybody have experience in this feild?
I'm looking to get some type of use of the 6th gear, shorten all of them yk.

My car is Fbo making 280whp and I feel a shorter gear ratio with definitely connect it a bit more.
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      07-30-2022, 07:01 AM   #2
Biginboca
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For the diff upgrade the only higher ratio oem diff you can swap is the 3.91 from an xdrive automatic, and yours is 3.73 (if you are rwd automatic). Other options are having a diff built like at diffsonline but that is pricey.

You have a dyno for 280whp, or if not how do you figure that is your whp?
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      07-30-2022, 01:22 PM   #3
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Xdrive diff.

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Originally Posted by Biginboca View Post
For the diff upgrade the only higher ratio oem diff you can swap is the 3.91 from an xdrive automatic, and yours is 3.73 (if you are rwd automatic). Other options are having a diff built like at diffsonline but that is pricey.

You have a dyno for 280whp, or if not how do you figure that is your whp?
Does the xdrive diff bolt in. Or is there fab work needed.

I did have a dyno but I lost my phone a few weeks back, go to get another next month anyway
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      07-30-2022, 06:38 PM   #4
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Quote:
Originally Posted by E90jacob View Post
Does the xdrive diff bolt in. Or is there fab work needed.

I did have a dyno but I lost my phone a few weeks back, go to get another next month anyway
There is minor fab work. You have to cut down a shaft sticking out of the pinion and swap the pinion flange from your oem diff. Nothing too hard frankly.
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      07-31-2022, 01:27 AM   #5
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Quote:
Originally Posted by Biginboca View Post
Quote:
Originally Posted by E90jacob View Post
Does the xdrive diff bolt in. Or is there fab work needed.

I did have a dyno but I lost my phone a few weeks back, go to get another next month anyway
There is minor fab work. You have to cut down a shaft sticking out of the pinion and swap the pinion flange from your oem diff. Nothing too hard frankly.
I may consider this, thank you so much. I was looking for more of a 4.44 ratio. I feel like a 3.91 from 3.73 would be noticable. Or worth the work
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      07-31-2022, 08:24 AM   #6
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Quote:
Originally Posted by E90jacob View Post
I may consider this, thank you so much. I was looking for more of a 4.44 ratio. I feel like a 3.91 from 3.73 would be noticable. Or worth the work
Honestly, 3.91 from 3.73 won’t make much difference. But you get there a lot cheaper than the 4.44
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      07-31-2022, 12:12 PM   #7
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Quote:
Originally Posted by Biginboca View Post
Quote:
Originally Posted by E90jacob View Post
I may consider this, thank you so much. I was looking for more of a 4.44 ratio. I feel like a 3.91 from 3.73 would be noticable. Or worth the work
Honestly, 3.91 from 3.73 won’t make much difference. But you get there a lot cheaper than the 4.44
I meant to say wouldn't*
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      07-31-2022, 12:25 PM   #8
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Quote:
Originally Posted by E90jacob View Post
I'm looking to upgrade my differential on my e90 328i AT.
Does anybody have experience in this feild?
I'm looking to get some type of use of the 6th gear, shorten all of them yk.

My car is Fbo making 280whp and I feel a shorter gear ratio with definitely connect it a bit more.
Like Boca said above, you can swap the xdrive 3,91. I did this on my 06 330i by swapping the rear driveshaft from the xdrive to direct bolt on to the differential.
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      07-31-2022, 08:38 PM   #9
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Quote:
Originally Posted by 303bmw View Post
Quote:
Originally Posted by E90jacob View Post
I'm looking to upgrade my differential on my e90 328i AT.
Does anybody have experience in this feild?
I'm looking to get some type of use of the 6th gear, shorten all of them yk.

My car is Fbo making 280whp and I feel a shorter gear ratio with definitely connect it a bit more.
Like Boca said above, you can swap the xdrive 3,91. I did this on my 06 330i by swapping the rear driveshaft from the xdrive to direct bolt on to the differential.
Could you notice a diff-erence. Pun intended lol
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      08-06-2022, 08:47 AM   #10
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Could you notice a diff-erence. Pun intended lol
Yes big time haha.
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