Will a 3.73 differential fit into a 2006 3.0si?

Harrison256 · 05-09-2017, 03:37 PM

I currently have the 3.23 differential in my car and wanted to swap up to the 3.73 which comes out of a N52 3.0i Z4.

The add I'm looking at says it will NOT fit any 3.0si models. Everything I've heard hear says otherwise.. that any differential is swappable with any other differential as long as its not an M. So who is correct?

Steeler · 05-09-2017, 06:09 PM

I fitted a 3.73 diff from a non M N52 with an SMG trans and it fit fine.
Why not ask the seller why they think it will not fit and post that reason here.
Some info below.

http://www.bokchoys.com/differential/GearRatios_E46.htm

TRiCC · 05-09-2017, 07:51 PM

All non m differentials across the BMW e46, x3, and z4 differentials swap over. All those chassis's share the same exact rear non m subframe. Yes the 3.73 from the n52 3.0i z4 will swap over like it was meant to be there. I swapped in a non m 3.46 e46 325i diff to my z4 3.0si no problem!

Quote:

Originally Posted by Harrison256

I currently have the 3.23 differential in my car and wanted to swap up to the 3.73 which comes out of a N52 3.0i Z4.

The add I'm looking at says it will NOT fit any 3.0si models. Everything I've heard hear says otherwise.. that any differential is swappable with any other differential as long as its not an M. So who is correct?

3002 tii · 05-10-2017, 06:53 AM

yes it'll fit, that's what I'm running now (3.46->3.73)!

2006E85 · 05-10-2017, 08:05 AM

I am still hunting for one. I swapped from 3.23 to 3.46, but I want MORE.

Harrison256 · 05-10-2017, 01:48 PM

Quote:

Originally Posted by 3002 tii

yes it'll fit, that's what I'm running now (3.46->3.73)!

How noticeable is the difference?

Harrison256 · 05-10-2017, 01:49 PM

Does anyone have a link to any useful DIYs on the actual differential swap. I'd like to attempt it on my own.

3002 tii · 05-10-2017, 04:54 PM

Quote:

Originally Posted by Harrison256

How noticeable is the difference?

I do notice a difference; it's a nice improvement but nothing drastic neither.

Spoke with few diff builders and general consensus is 5% isn't worth it, 10%+ is when u get that kick in pants feeling but may come at the expense of driveability. Going from 3.46 to 3.73 was ~8% increase and I would say it's just right. On track it keeps my revs in the sweet spot especially when powering out of turns. Yet for everyday driving I don't find it to be any less practical. Can still cruise in 6th on the freeway and start from 2nd gear easier at a light if you're feeling lazy.

Steeler · 05-10-2017, 04:57 PM

^^
Just to tack on, first gear is basically useless with the 3.73.
RPM @ 70mph is around 2900 rpm with 265/35/18 and 6 speed.

WickedNy · 05-11-2017, 04:27 PM

Had gotten into an argument with an auto scrap yard because they tried giving me the same bs, after 10 minutes of arguing back and forth the place refused to sell it to me. Most places have not a shits clue, this forum is filled with knowledge beyond what some "experts" thought on it is...I have 3.73 in si as well, it fits

Harrison256 · 05-11-2017, 06:06 PM

Quote:

Originally Posted by WickedNy

Had gotten into an argument with an auto scrap yard because they tried giving me the same bs, after 10 minutes of arguing back and forth the place refused to sell it to me. Most places have not a shits clue, this forum is filled with knowledge beyond what some "experts" thought on it is...I have 3.73 in si as well, it fits

Do you have any regrets? Is first gear ridiculously short or is it still daily driveable

WickedNy · 05-11-2017, 09:37 PM

Zero regrets, def easily still drivable without any increase in aggravation

2006E85 · 05-18-2017, 03:03 PM

Harrison256

Did you get it?

peter82 · 01-12-2018, 08:30 PM

Hi guys, i am looking for diff for 2006 Z4 Si in manual trans. I am not sure if i understand it correctly so my simple question is: Will the diff from Z4 3.0si 3.73 Gear Ratio Automatic fit in MANUAL?
Thank you for your help.

Steeler · 01-13-2018, 08:45 AM

Quote:

Originally Posted by peter82

Hi guys, i am looking for diff for 2006 Z4 Si in manual trans. I am not sure if i understand it correctly so my simple question is: Will the diff from Z4 3.0si 3.73 Gear Ratio Automatic fit in MANUAL?
Thank you for your help.

Quote:

Originally Posted by dbarton62

I fitted a 3.73 diff from a non M N52 with an SMG trans and it fit fine.
Why not ask the seller why they think it will not fit and post that reason here.
Some info below.

http://www.bokchoys.com/differential/GearRatios_E46.htm

Yes

05-09-2017, 03:37 PM	#1
Harrison256 Enlisted Member 1 Rep 33 Posts Drives: 2006 BMW Z4 3.0si Join Date: Mar 2017 Location: Houston, TX iTrader: (0)	Will a 3.73 differential fit into a 2006 3.0si? I currently have the 3.23 differential in my car and wanted to swap up to the 3.73 which comes out of a N52 3.0i Z4. The add I'm looking at says it will NOT fit any 3.0si models. Everything I've heard hear says otherwise.. that any differential is swappable with any other differential as long as its not an M. So who is correct? __________________ 2006 Z4 3.0Si
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05-09-2017, 06:09 PM	#2
Steeler Colonel 2428 Rep 2,704 Posts Drives: Built not Bought 04 Z4 VF Join Date: Feb 2013 Location: Kitchener Ontario Canada iTrader: (2)	I fitted a 3.73 diff from a non M N52 with an SMG trans and it fit fine. Why not ask the seller why they think it will not fit and post that reason here. Some info below. http://www.bokchoys.com/differential/GearRatios_E46.htm
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05-10-2017, 06:53 AM	#4
3002 tii Lieutenant General 2282 Rep 12,565 Posts Drives: Z4 M, X5, GX460 Join Date: Apr 2008 Location: CT iTrader: (99) Garage List F15 X5 xDrive35i [8.75] E86 Z4 M [10.00] F10 550i (Retired) [9.17] F25 X3 xDrive35i (R ... [9.43] E82 135is (Retired) [9.50] E85 Z4 M (Retired) [9.41] E90 328i xDrive (Re ... [9.25] E86 Z4 3.0si (Retired) [9.22]	yes it'll fit, that's what I'm running now (3.46->3.73)! __________________ Follow for latest mods
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05-10-2017, 08:05 AM	#5
2006E85 Private First Class 12 Rep 104 Posts Drives: 3.0si Roadster Join Date: Jun 2014 Location: Puerto Rico iTrader: (0) Garage List 2006 BMW Z4 [0.00]	I am still hunting for one. I swapped from 3.23 to 3.46, but I want MORE. __________________ 2006 Z4 3.0si, 6MT RPI Intake Scoop, K
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05-10-2017, 01:49 PM	#7
Harrison256 Enlisted Member 1 Rep 33 Posts Drives: 2006 BMW Z4 3.0si Join Date: Mar 2017 Location: Houston, TX iTrader: (0)	Does anyone have a link to any useful DIYs on the actual differential swap. I'd like to attempt it on my own. __________________ 2006 Z4 3.0Si
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05-10-2017, 04:57 PM	#9
Steeler Colonel 2428 Rep 2,704 Posts Drives: Built not Bought 04 Z4 VF Join Date: Feb 2013 Location: Kitchener Ontario Canada iTrader: (2)	^^ Just to tack on, first gear is basically useless with the 3.73. RPM @ 70mph is around 2900 rpm with 265/35/18 and 6 speed. __________________ W2A Intercooled Vortech V3Si, custom ducting, Alpha N, 60# Bosch,2.62 pulley, multi port WMI, Severn Tuning(pokeybritches), Tial, magnaflow,SS race muffler, 42 design,3.91LSD, H&R, Hotchkis,ST coils,Konis, Megan camber arms, AKG SS, Nylon mounts, Poly bushings, Carbon interior, CF Aero.APEX
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05-11-2017, 04:27 PM	#10
WickedNy Get Some 225 Rep 759 Posts Drives: 07 Z4 3.0si Join Date: Jan 2012 Location: Long Island iTrader: (1) Garage List 07 z4 3.0si [0.00]	Had gotten into an argument with an auto scrap yard because they tried giving me the same bs, after 10 minutes of arguing back and forth the place refused to sell it to me. Most places have not a shits clue, this forum is filled with knowledge beyond what some "experts" thought on it is...I have 3.73 in si as well, it fits
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05-11-2017, 09:37 PM	#12
WickedNy Get Some 225 Rep 759 Posts Drives: 07 Z4 3.0si Join Date: Jan 2012 Location: Long Island iTrader: (1) Garage List 07 z4 3.0si [0.00]	Zero regrets, def easily still drivable without any increase in aggravation
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05-18-2017, 03:03 PM	#13
2006E85 Private First Class 12 Rep 104 Posts Drives: 3.0si Roadster Join Date: Jun 2014 Location: Puerto Rico iTrader: (0) Garage List 2006 BMW Z4 [0.00]	Harrison256 Did you get it? __________________ 2006 Z4 3.0si, 6MT RPI Intake Scoop, K
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01-12-2018, 08:30 PM	#14
peter82 New Member 0 Rep 5 Posts Drives: BMW Z4 3.0Si Join Date: Nov 2015 Location: California iTrader: (0)	Manual trans. Hi guys, i am looking for diff for 2006 Z4 Si in manual trans. I am not sure if i understand it correctly so my simple question is: Will the diff from Z4 3.0si 3.73 Gear Ratio Automatic fit in MANUAL? Thank you for your help.
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