Another 6at to dct conversion

DirtKurt

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What's up everyone, I'm currently collecting parts to convert my 2009 335i 6AT to DCT. I've been re searching for awhile and feel like I have a pretty good grasp on most of what's involved.
Currently have on hand a 335is dct transmission out of a 2011 w/44k miles, the entire shifter assembly , with wiring pigtails, and a mfactory 8 bolt lightweight flywheel. Still haven't pulled the trigger on a rear differential, transmission harness and possibly a steering wheel.

I have some questions that I'm hoping some of the more experienced can help me with. I would like to upgrade the diff to something more stout instead of just a standard 2.56 with a lsd. The concencus seems to be that anything within 10% of the factory is OK. What I'm not clear on is if the performance is negatively affected the further from 2.56 you get? I have my eye on a 2.77 setup but don't want to put the work in if I'm going to end up with something that just works mediocre.

Thanks for any insight, hoping to use this thread to document the conversion and ask questions over the winter
20181017_163148.jpg 20181010_212847.jpg 20181020_143850.jpg
 
Nov 18, 2017
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#2
What's up everyone, I'm currently collecting parts to convert my 2009 335i 6AT to DCT. I've been re searching for awhile and feel like I have a pretty good grasp on most of what's involved.
Currently have on hand a 335is dct transmission out of a 2011 w/44k miles, the entire shifter assembly , with wiring pigtails, and a mfactory 8 bolt lightweight flywheel. Still haven't pulled the trigger on a rear differential, transmission harness and possibly a steering wheel.

I have some questions that I'm hoping some of the more experienced can help me with. I would like to upgrade the diff to something more stout instead of just a standard 2.56 with a lsd. The concencus seems to be that anything within 10% of the factory is OK. What I'm not clear on is if the performance is negatively affected the further from 2.56 you get? I have my eye on a 2.77 setup but don't want to put the work in if I'm going to end up with something that just works mediocre.

Thanks for any insight, hoping to use this thread to document the conversion and ask questions over the winter
You can actually run any diff ratio you want as long as its a 335 or M3 ratio +-10%

You can convert to 335i DTC or M3 DCT
The vibe i got was that if you're converting to DCT dont go straight to M3 DCT for the ratio. Complete the conversion and then go the next step. Each step has complications and the guru's for this are @LMB335is @dyezak and @Bimaxtremeretro
 

DirtKurt

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#3
You can actually run any diff ratio you want as long as its a 335 or M3 ratio +-10%

You can convert to 335i DTC or M3 DCT
The vibe i got was that if you're converting to DCT dont go straight to M3 DCT for the ratio. Complete the conversion and then go the next step. Each step has complications and the guru's for this are @LMB335is @dyezak and @Bimaxtremeretro

Thanks, thats what I was hoping to hear. Anyone else have any experience with different ratios?
 
Apr 12, 2017
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#4
Thanks, thats what I was hoping to hear. Anyone else have any experience with different ratios?
It really comes down to what software you ultimately want to run (335is or M3/GTS), power goals, and your budget IMO. I'm currently running M3 GTS software with the M3 drivetrain (axles, DS, and diff w/ custom 2.81 gearing). This is probably the upper end dollar wise but gave me everything that I wanted this car to be.

Staying with 335is software will limit you to 335is gearing and drivetrain for the most part. You could use a 215mm 2.81 FD from a 335d and it will work. Probably the cheapest solution. You could move up to the M3 drivetrain with a 210mm 2.81 FD from 80's V8 BMW's and retain the M3 LSD and diff, axles, and DS (needs to be shortened) and substantially increase the drivetrain strength in the process. This would also work with the 335is software.

The M3 software will require the M3 GWS, center console pieces, switches, etc., some repinning of connectors, flashing, coding. You'd need the M3 drivetrain and the M3 diff could be geared from 2.81 to 3.23 with the available R&P's out there, but it's not a cheap conversion. You would get all the benefits of the M3 software though, faster shifts, adjustable launch control, no need to hold the brake while stopped.

This is just a quick overview of what I picked up while researching for my car. If you have any specific questions I'd be happy to help if I can.
 

hydra

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Jan 31, 2017
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#5
Is it correct to assume that the 335is software will command higher clamping pressure and thus hold more torque than the M3 software though?
 
Apr 12, 2017
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#6
Is it correct to assume that the 335is software will command higher clamping pressure and thus hold more torque than the M3 software though?
I see higher reported torque values with the M3 GTS software (900nm-950nm) than I did on 335is software (790nm-850nm) with the same tune and load to torque tables
 

hydra

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#7
Does this mean the torque capacity of the transmission is higher? Because according to BMW's own documentation the internal torque capacity of the M3/M4/335is DCT is higher, not sure if this is due to different software or hardware though.
 

jyamona

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#8
I see higher reported torque values with the M3 GTS software (900nm-950nm) than I did on 335is software (790nm-850nm) with the same tune and load to torque tables
Where are you logging these values?
 

jyamona

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#10
Isn't that the torque actual value nm in MHD?
Yea, I am just surprised to see a change in the logged value simply by running a different TCU flash. That value is reported to the TCU from the DME.
 
Apr 12, 2017
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#11
Yea, I am just surprised to see a change in the logged value simply by running a different TCU flash. That value is reported to the TCU from the DME.
Me too. It was a nice surprise.
 

jyamona

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#12
Are you able to back to back compare that? I'm curious if something else influenced the higher number.
 

DirtKurt

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#13
It really comes down to what software you ultimately want to run (335is or M3/GTS), power goals, and your budget IMO. I'm currently running M3 GTS software with the M3 drivetrain (axles, DS, and diff w/ custom 2.81 gearing). This is probably the upper end dollar wise but gave me everything that I wanted this car to be.

Staying with 335is software will limit you to 335is gearing and drivetrain for the most part. You could use a 215mm 2.81 FD from a 335d and it will work. Probably the cheapest solution. You could move up to the M3 drivetrain with a 210mm 2.81 FD from 80's V8 BMW's and retain the M3 LSD and diff, axles, and DS (needs to be shortened) and substantially increase the drivetrain strength in the process. This would also work with the 335is software.

The M3 software will require the M3 GWS, center console pieces, switches, etc., some repinning of connectors, flashing, coding. You'd need the M3 drivetrain and the M3 diff could be geared from 2.81 to 3.23 with the available R&P's out there, but it's not a cheap conversion. You would get all the benefits of the M3 software though, faster shifts, adjustable launch control, no need to hold the brake while stopped.

This is just a quick overview of what I picked up while researching for my car. If you have any specific questions I'd be happy to help if I can.
Thanks for the reply, you kind of have me leanings towards the m3 gts tune now. Do I need the gauge cluster as well? I've decided I don't want to spend the money on building a 2.56 diff to still end up with a weak unit. I'd rather spend the money re gearing a m3 unit.
It really comes down to what software you ultimately want to run (335is or M3/GTS), power goals, and your budget IMO. I'm currently running M3 GTS software with the M3 drivetrain (axles, DS, and diff w/ custom 2.81 gearing). This is probably the upper end dollar wise but gave me everything that I wanted this car to be.

Staying with 335is software will limit you to 335is gearing and drivetrain for the most part. You could use a 215mm 2.81 FD from a 335d and it will work. Probably the cheapest solution. You could move up to the M3 drivetrain with a 210mm 2.81 FD from 80's V8 BMW's and retain the M3 LSD and diff, axles, and DS (needs to be shortened) and substantially increase the drivetrain strength in the process. This would also work with the 335is software.

The M3 software will require the M3 GWS, center console pieces, switches, etc., some repinning of connectors, flashing, coding. You'd need the M3 drivetrain and the M3 diff could be geared from 2.81 to 3.23 with the available R&P's out there, but it's not a cheap conversion. You would get all the benefits of the M3 software though, faster shifts, adjustable launch control, no need to hold the brake while stopped.

This is just a quick overview of what I picked up while researching for my car. If you have any specific questions I'd be happy to help if I can.
Thanks man, I will have alot of questions im sure. Does the m3 gts setup have the same restrictions with the gearing +/- 10% that the 335is software has? You have me leaning towards the m3 setup now
 
Apr 12, 2017
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#14
Are you able to back to back compare that? I'm curious if something else influenced the higher number.
I have logs from a Wannagofast 1/2 mile event in January on 335is software before the conversion and logs from another event a couple weeks ago with the M3 GTS software and full conversion. I'll post the links for you, maybe it will help. The recent logs are on a one revision newer map but I can't tell you offhand what changes were made. Max TQ was 900nm before, now topping 950nm. Reach out to Dimitri (BQ Tuning), he'd be able to tell you what was changed between the two maps. He's interested in a IMK0S ROM swap as well so maybe you can kill three birds with one stone.

https://datazap.me/u/veloman62/wannagofast?log=0&data=3-19 M3 GTS logs

https://datazap.me/u/veloman62/bqe60ina0sdctbeta15mhd-wannagofast-runs-1-3-012018 335is logs
 
Apr 12, 2017
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#15
Thanks for the reply, you kind of have me leanings towards the m3 gts tune now. Do I need the gauge cluster as well? I've decided I don't want to spend the money on building a 2.56 diff to still end up with a weak unit. I'd rather spend the money re gearing a m3 unit.


Thanks man, I will have alot of questions im sure. Does the m3 gts setup have the same restrictions with the gearing +/- 10% that the 335is software has? You have me leaning towards the m3 setup now
The cluster isn't a requirement but it does look damn good. I found a really low mileage diff (under 30k miles) for $350, I got lucky. The 2.81 R&P cost $300, and I elected to replace all the seals and bearings while my guy was in there so I probably have $1k-1.2k in it buts it's factory fresh and way cheaper than I could of bought it from diffsonline especially with the $1500 core charge.

My 2.81 is outside the +/- 10% and it works fantastic with the GTS flash but it's probably as high as you can go without having issues. I do 1/2 mile event so I didn't want to give up too much up top. On stock turbos I can run through the traps in 6th at around 6.2k rpm, not ideal but better than hitting 7th...I think. Upgraded turbos would solve that issue. A 2.93 gear is available but the last thing you really need is more torque multiplied down low.
 
Mar 10, 2018
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#16
You may want to start with the oem flywheel. I can't use D mode due to vibrations in high gear, high load low rpm scenarios after swapping to the M4 flywheel. Only drive in S and M mode now to keep the revs up.
 

doublespaces

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#17
You may want to start with the oem flywheel. I can't use D mode due to vibrations in high gear, high load low rpm scenarios after swapping to the M4 flywheel. Only drive in S and M mode now to keep the revs up.
I've heard of a couple reports of the M4 flywheel not working... He has the 8 bolt so this is his only option besides the OEM flywheel. I'm curious if the problem will be better or worse.
 

DirtKurt

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#18
You may want to start with the oem flywheel. I can't use D mode due to vibrations in high gear, high load low rpm scenarios after swapping to the M4 flywheel. Only drive in S and M mode now to keep the revs up.
I could definitely understand this being an issue, it's really no different than running a mt with a lightweight single mass flywheel. Is anyone out there running the mfactory flywheel yet?
 

DirtKurt

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#19
Got my shifter assembly in finally, came with the connectors and some wiring which is sweet. Unfortunately the rest is kind of a mess and the park detent cable is damaged :anguished:.
Are any of you guys that have done the m3 conversion interested in selling your stock shift assembly? not having much luck on ebay lately.
 

doublespaces

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#20
Got my shifter assembly in finally, came with the connectors and some wiring which is sweet. Unfortunately the rest is kind of a mess and the park detent cable is damaged :anguished:.
Are any of you guys that have done the m3 conversion interested in selling your stock shift assembly? not having much luck on ebay lately.
The GWS? I have one but just don't have the shift knob. I was thinking about using it even though I have the M3 stuff. Kinda wanted to take it one step at a time. I may change my mind though. Try the junk yards, they are usually pretty decent.
 

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