135i N55 DCT - Possible to swap in an M3 DCT differential?

MilkBags · 02-27-2018, 10:34 AM

Hello,

I know this topic has been covered a lot for 135i/335i but with MT and some AT but I haven't found any clear answer about DCT with the 2.56 FD.

I read a lot about people who have done it (here for example) and I know I'd need a custom-made driveshaft, axle shafts as well as the differential from a DCT M3 itself. I can get those easily and for a good price.

I understand the M3 DCT differential has a FD of 3.15 which line-up pretty well with the x35i MT FD of 3.08, but would it work with my 2.56 FD or would it have any issues shifting at the right RPMs? Or any other issues whatsoever? Asking because this thread mention shfiting issues with a 3.08 diff in a N55 DCT. I understand my top speed would be lower with a 3.15 ratio as well, but that's fine.

Thank you!

The Wind Breezes · 02-27-2018, 10:55 AM

Sounds like a lot of hassle just to get a mediocre diff. Getting your choice of clutch pack internals or even welding it would both be better options.

dane083 · 02-28-2018, 06:18 PM

Quote:

Originally Posted by The Wind Breezes

Sounds like a lot of hassle just to get a mediocre diff. Getting your choice of clutch pack internals or even welding it would both be better options.

A welded diff in a BMW, seriously that's the advice you give?

Gizmo135i · 03-01-2018, 01:14 PM

If people are having issues with a 3.08 then i would think a 3.15 would be even worse since the ratio is even further away from stock.

kivyee · 03-02-2018, 09:18 PM

Not sure about the physical compatibility of the differential, but the issue with swapping a different gear ratio differential in the DCT is that you will get errors from the DCT control unit seeing different speeds from what it is expecting. Someone tried it on one of the forums and ended up swapping back due to the unhappy DCT.

02-27-2018, 10:34 AM	#1
MilkBags Registered 0 Rep 2 Posts Drives: 2011 135i DCT Join Date: Feb 2018 Location: Montreal iTrader: (0)	135i N55 DCT - Possible to swap in an M3 DCT differential? Hello, I know this topic has been covered a lot for 135i/335i but with MT and some AT but I haven't found any clear answer about DCT with the 2.56 FD. I read a lot about people who have done it (here for example) and I know I'd need a custom-made driveshaft, axle shafts as well as the differential from a DCT M3 itself. I can get those easily and for a good price. I understand the M3 DCT differential has a FD of 3.15 which line-up pretty well with the x35i MT FD of 3.08, but would it work with my 2.56 FD or would it have any issues shifting at the right RPMs? Or any other issues whatsoever? Asking because this thread mention shfiting issues with a 3.08 diff in a N55 DCT. I understand my top speed would be lower with a 3.15 ratio as well, but that's fine. Thank you!
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02-27-2018, 10:55 AM	#2
The Wind Breezes Lieutenant Colonel 912 Rep 1,850 Posts Drives: 135i N55 DCT Join Date: Apr 2015 Location: USA iTrader: (0)	Sounds like a lot of hassle just to get a mediocre diff. Getting your choice of clutch pack internals or even welding it would both be better options.
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03-01-2018, 01:14 PM	#4
Gizmo135i Second Lieutenant 116 Rep 264 Posts Drives: 135i n55 Join Date: May 2016 Location: Park Ridge NJ iTrader: (0)	If people are having issues with a 3.08 then i would think a 3.15 would be even worse since the ratio is even further away from stock.
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03-02-2018, 09:18 PM	#5
kivyee Private First Class 99 Rep 160 Posts Drives: 2017 230ix Track Pack Join Date: Jan 2018 Location: Vancouver iTrader: (0)	Not sure about the physical compatibility of the differential, but the issue with swapping a different gear ratio differential in the DCT is that you will get errors from the DCT control unit seeing different speeds from what it is expecting. Someone tried it on one of the forums and ended up swapping back due to the unhappy DCT.
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