3.46 diff for ST

diolev

Lurker
Dec 20, 2019
12
5
0
Ride
09 335i
Thinking this might help for city driving. Anybody have impressions for street? Any nutters swap the non lsd auto in there? Is it a direct swap? Also thinking since I have the stg3+ clutch the 3.46 might be easier to modulate the clutch. It seems you gotta rev extra for the clutch and stl ltw flywheel. It's definitely hard to engage smoothly some of the time. Not sure if it would have any effect.

Also my tuner hasnt finished targeting boost, which once we finish, then he will alter timing (and vanos?) Which could make it have more low-end but not sure how much.
 

doublespaces

Administrator
Oct 18, 2016
9,303
4,332
0
AZ
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2009 E93 335i
I know several people have swapped to the 3.46 and from what I recall, most people have ended up not liking it. But I could be remembering incorrectly.
 

135i2

Specialist
Jul 23, 2017
98
97
0
Ride
135i
I run a 3.15 full M3 V8 rear end in a 135 auto which is about right for high powered ST. Have also run the 3.85 for a while.
 

Torgus

Brigadier General
Nov 6, 2016
2,671
2,194
0
Boston
Ride
ACF 6466 E92 + METH
I run a 3.15 full M3 V8 rear end in a 135 auto which is about right for high powered ST. Have also run the 3.85 for a while.

What was 3.85 like? I mean I can imagine but curious.


ModelPlatformTypeTransmission
1​
2​
3​
4​
5​
6​
reverse​
final drive​
redline​
335iE92Coupemanual
4.06

2.4

1.58

1.19

1.00

0.87

3.68

3.08

7200
 

135i2

Specialist
Jul 23, 2017
98
97
0
Ride
135i
First gear with a 3.85 and ST was just OK to get flying and get some early spool on board but its an immediate fast shift.
Made every other gear except top gear driveable. Around 2400rpm at 110kmh from memory, just is an annoying NVH zone. Over 2500rpm started to sound and feel sweeter.

Bare in mind that Oz has low speed limits at 100 and 110km/h (68mph for the imperialists).
Round town stuff was fine as you rarely get over 35-45mph.

3.15 means highway cruising out of the city is relaxed and I can get better use of 1st.
Apparently the 3.15 will be better for a 1/4 mile run.
It does mean crazy fast logs but admittedly its more stable acceleration than the even more extreme slingshot of a 3.85
 
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Bmwfixerguy1

Lieutenant
Jun 5, 2017
875
292
0
Ride
07 335i MT
That's interesting, I knew the 3.46 was always regretted by all parties who ventured but never thought of the m3 lsd being geared a little tighter bit not as tight as the auto pumpkin

I haven't looked into it in awhile... What all is needed for an e9x m3 diff swap, is anyone selling install kits like driveshaft ECT.

I don't see many of than In the shop anymore but I thought the subframe mounting points were different . But I might be thiking of all the F M cars
 

ShocknAwe

Captain
Jan 24, 2018
1,499
1
742
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Charleston, SC
Ride
N54/3 1er ///Mutt
I'm sure it doesn't compare since I'm 6MT on twins but I went from 3.08 on my first LSD to 3.46 on my new one. Love it. I actually don't use 1st much anymore which gives the car a nice dog leg 5 speed feel.

Road course in the 3-4-5 band which gets rid of the annoying 2 to 3 shift. Cruising at higher rpm on highway not an issue currently, we'll see with time I guess.
 

berns

Corporal
Jan 15, 2018
175
266
0
Ride
'09 135i
I love the 3.46 for the track and for city driving, but hate it on the freeway because 6th gear at 80mph sucks now.
 
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diolev

Lurker
Dec 20, 2019
12
5
0
Ride
09 335i
I love the 3.46 for the track and for city driving, but hate it on the freeway because 6th gear at 80mph sucks now.
My drive to work is about 10 minutes on freeway and 5 city. So I'm not seeing alot of freeway usually. I'm thinking of fun factor increase and would like it a lil faster while the engine is cold/below 3.5k. Cause most my driving day to day is waiting for it to warm up unfortunately, though fortunately it nice to have a short commute.
 

135itp

Private
Dec 6, 2018
34
28
0
Ride
09 135i n54 AT
I love the 3.46 for the track and for city driving, but hate it on the freeway because 6th gear at 80mph sucks now.

Hey Berns (or anyone else reading who has swapped diffs) did you notice a difference in length in the driveshaft during the install? Did you pull the driveshaft forward a little like this (see pics)

I’m doing this swap now and seems like it works but not sure if this amount of stretch is ok. Seems like it’s the only way to make it work.

This difference for a 135i is 2mm between the auto and manual driveshaft. Does not make a difference which driveshaft is used here.

Appreciate your input in advance
 

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