Manual RWD 3.23 to 3.91 swap

astigpangit · 07-23-2024, 03:00 PM

hi, manual rwd 328i here with stock 3.23 diff. i want to confirm that a REAR 3.91 DIFF is a direct bolt on?

chilledn52 · 07-23-2024, 03:13 PM

no, you will have to swap the mounting flange for the driveshaft.

Ohio Enthusiast · 07-23-2024, 03:14 PM

I'm not an expert, but as far as I know the 3.91 diff is on the automatic xDrive. Not sure if it's compatible with the RWD driveshaft.
You might find it easier to swap to the 3.73 diff from the RWD automatic, which should be a direct swap.

astigpangit · 07-23-2024, 03:17 PM

Quote:

Originally Posted by chilledn52

no, you will have to swap the mounting flange for the driveshaft.

do you mean the giubo? or the center support bearing? or is it something else

chilledn52 · 07-23-2024, 03:53 PM

Quote:

Originally Posted by astigpangit

do you mean the giubo? or the center support bearing? or is it something else

The input flange for the differential. I believe 3.91 is a 3 bolt flange, RWD differentials are 4 bolt flange

nour.v10 · 07-23-2024, 04:40 PM

I was thinking of doing a manual swap on my 335xi. Seems that xdrive does not have the same drivetrain as any of the manual transmissions. (RWD)

07-23-2024, 03:00 PM	#1
astigpangit New Member 5 Rep 20 Posts Drives: 2011 328i base package Join Date: Jun 2024 Location: Pacific Northwest iTrader: (0)	Manual RWD 3.23 to 3.91 swap hi, manual rwd 328i here with stock 3.23 diff. i want to confirm that a REAR 3.91 DIFF is a direct bolt on?
	Appreciate 0 Tweet Quote

07-23-2024, 03:13 PM	#2
chilledn52 Parts Pro 129 Rep 166 Posts Drives: 2007 BMW 328xi 6MT Join Date: Sep 2022 Location: Alberta iTrader: (0) Garage List 2007 BMW 328xi [10.00]	no, you will have to swap the mounting flange for the driveshaft. __________________ E90 328xi 6MT \| Intake Scoops \| K&N + Charcoal Filter Delete \| DIY Dinan 3in \| 3.25in + 3.5in piping \| N54 Manifold \| Ceramic Coated Headers \| Secondary Cat Delete \| Xdelete \| 3.91 Diffs \| 22RPD Tune
	Appreciate 0 Quote

07-23-2024, 03:14 PM	#3
Ohio Enthusiast Private 68 Rep 63 Posts Drives: '11 E93 335i, '18 BRZ Join Date: May 2024 Location: Dayton, OH iTrader: (0)	I'm not an expert, but as far as I know the 3.91 diff is on the automatic xDrive. Not sure if it's compatible with the RWD driveshaft. You might find it easier to swap to the 3.73 diff from the RWD automatic, which should be a direct swap.
	Appreciate 0 Quote

07-23-2024, 04:40 PM	#6
nour.v10 Registered 0 Rep 3 Posts Drives: BMW 335xi N55 2013 e92 Join Date: Jul 2024 Location: Kentucky iTrader: (0)	I was thinking of doing a manual swap on my 335xi. Seems that xdrive does not have the same drivetrain as any of the manual transmissions. (RWD)
	Appreciate 0 Quote