F30 Changing Gearing

VAF30 · 03-16-2019, 11:00 AM

Greetings...
Time to look at LSD Diffs .. and since my car.. 2014 335i 8AT is factory at 3.15 in the diff.. if I change to 3.45 or so is there any coding required in the engine or tranny or? to support the diff gearing change?

Thank for the assist!

VAF30 · 03-17-2019, 12:20 PM

Any thoughts out there?

zinner · 03-18-2019, 08:44 AM

I haven't seen an option/solution to change the rear gear ratio. Probably best to ask the people selling it to you what they recommend. Might not have to do anything ?

doodlebro · 03-18-2019, 05:21 PM

Definitely going to need it for the speedo to read right.

bradsm87 · 03-18-2019, 05:27 PM

There are settings in both the DME and TCU ROM for final drive ratio. I don't know how important/necessary they are though.

VAF30 · 03-20-2019, 12:18 PM

First -- Thanks for the input!!!

From what I have been able to learn.. for Manual cars -- no change in any SW .. bolt it in ang go.. no issues

For - Auto -- not recommended .. custom tuning can probably get around the change but both have suggested not too... I've got a reply from...

So looks like Ill be staying at 3.15 factory for auto unless I can find someone whos actually done it..

XutvJet · 03-20-2019, 04:11 PM

Yeah, you'll need to keep the stock ratio. We recently had a guy on the 2 series forum accidentally install a M240 automatic LSD into his M235 automatic. The M240 autos use a taller 2.80 gear vs the M235's automatic 3.08 gearset and the DME and transmission computer were throwing speed errors on the highway and I believe shift timing was a bit off. He looked into coding, but he couldn't find a tuner capable of addressing the issue.

03-16-2019, 11:00 AM	#1
VAF30 Private 26 Rep 75 Posts Drives: 14' F30 335i Join Date: Jul 2018 Location: Richmond VA iTrader: (0)	F30 Changing Gearing - Coding required? Greetings... Time to look at LSD Diffs .. and since my car.. 2014 335i 8AT is factory at 3.15 in the diff.. if I change to 3.45 or so is there any coding required in the engine or tranny or? to support the diff gearing change? Thank for the assist!
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03-17-2019, 12:20 PM	#2
VAF30 Private 26 Rep 75 Posts Drives: 14' F30 335i Join Date: Jul 2018 Location: Richmond VA iTrader: (0)	Any thoughts out there?
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03-18-2019, 08:44 AM	#3
zinner Major 559 Rep 1,127 Posts Drives: `17 X5 35d/`15 335i/`18 M550IX Join Date: Oct 2014 Location: Raleigh, NC iTrader: (0)	I haven't seen an option/solution to change the rear gear ratio. Probably best to ask the people selling it to you what they recommend. Might not have to do anything ?
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03-18-2019, 05:21 PM	#4
doodlebro Lieutenant 121 Rep 470 Posts Drives: '17 X3 35i Join Date: Mar 2017 Location: Denver iTrader: (1)	Definitely going to need it for the speedo to read right. __________________ Current mods Rockford Fosgate P3 // JBL MS-A5001 // MiniDSP Ultra Racing Strut Brace // AFe Pro Dry S // PS2 // Custom Inlet // DV+ // FTP Boost Pipes // VRSF Race IC // VRSF Downpipe // ECUTek Protune @ 5280'
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03-18-2019, 05:27 PM	#5
bradsm87 Lieutenant Colonel 595 Rep 1,693 Posts Drives: F25 LCI xDrive30d Join Date: Jun 2013 Location: Australia iTrader: (0)	There are settings in both the DME and TCU ROM for final drive ratio. I don't know how important/necessary they are though.
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03-20-2019, 12:18 PM	#6
VAF30 Private 26 Rep 75 Posts Drives: 14' F30 335i Join Date: Jul 2018 Location: Richmond VA iTrader: (0)	First -- Thanks for the input!!! From what I have been able to learn.. for Manual cars -- no change in any SW .. bolt it in ang go.. no issues For - Auto -- not recommended .. custom tuning can probably get around the change but both have suggested not too... I've got a reply from... So looks like Ill be staying at 3.15 factory for auto unless I can find someone whos actually done it..
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03-20-2019, 04:11 PM	#7
XutvJet Major General 5551 Rep 5,369 Posts Drives: 2011 Cayman Base, 2016 M235 Join Date: Mar 2016 Location: Kansas City iTrader: (-1)	Yeah, you'll need to keep the stock ratio. We recently had a guy on the 2 series forum accidentally install a M240 automatic LSD into his M235 automatic. The M240 autos use a taller 2.80 gear vs the M235's automatic 3.08 gearset and the DME and transmission computer were throwing speed errors on the highway and I believe shift timing was a bit off. He looked into coding, but he couldn't find a tuner capable of addressing the issue. __________________ The forest was shrinking, but the Trees kept voting for the Axe, for the Axe was clever and convinced the Trees that because his handle was made of wood, he was one of them.
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