Any DCT owners changed their final drive / diff ratio?

[Martyn]

As per the title, anyone done this? What ratio did you go for and are you finding your DCT behaves?

[tdott]

I have not done this, but it is a mod that guys do. and I might be interested if there was a solution to fix the issues.

DCT cars have a 3.154 Ratio, and manual cars have a 3.846 diff. Swapping a manual diff in a DCT car is a common mod, 4.10 motorsports gears are a common mod for manual cars.

There is an issue with the manual diff in the DCT car where downshifts are no longer smooth and the auto mode doesn't work as well.
AFAIK there is someone offering a software change to fix it, but only came to light recently and I believe they charge a lot to change the diff ratio software wise.

Dinan offered a 3.45 ratio to DCT cars back in the days, but never was able to reprogram the car to shift right.
I believe guys have also built a custom setup with 3.62 gear sets from an E39 m5 diff. As well as fitting the clutch type lsd from the m5 into the e9xm3 diff.

[Martyn]

I believe I have located the final drive ratio in the MSS60 so I need someone with swapped gears to try it. I did have someone who had fitted a 3.62 in their E92 but he has other issues at the moment.

[terra]

I believe I have located the final drive ratio in the MSS60 so I need someone with swapped gears to try it. I did have someone who had fitted a 3.62 in their E92 but he has other issues at the moment.

From what I'm seeing, there needs to be something edited within the transmission software itself (in fact 335 guys sometimes will flash M3 DCT software so that they can run the M3 ratio).

[Martyn]

Yeah, i've seen similar too. I wonder why in the MSS60 manual, SMG and DCT ratios are defined and in the MSS65 manual and SMG ratios are defined if they aren't used....

[terra]

Yeah, i've seen similar too. I wonder why in the MSS60 both manual, SMG and DCT ratios are defined and in the MSS65 manual and SMG ratios are defined if they aren't used....

Could be for other functions like cruise control or shift lights. Though idk why the SMG ratios would be there.

[tdott]

I believe changes are in the DCT module also, GTS software on a regular M3 is a popular mod. One of the first guys that claimed to have been able to change the ratios says he starts with the GTS software and makes his changes.

[Peter De La Mare]

I went 3.62 a couple of years ago. The downshift blips disappeared as expected. TRS Performance in the UK tweaked the map to reflect the ratio change. Now back to normal.

[Tomba]

xHP currently supports some DCT transmission and adds the possibility to change the final drive ratio.
Unfortunately I don't have an A2L file for the DCT transmission. I can read it with X17/Flex tool (MagicMotorsport). But don't know the location/value to edit.

In attachment DKG/DCT read from E9X M3.

[olza]

xHP currently supports some DCT transmission and adds the possibility to change the final drive ratio.
Unfortunately I don't have an A2L file for the DCT transmission. I can read it with X17/Flex tool (MagicMotorsport). But don't know the location/value to edit.

In attachment DKG/DCT read from E9X M3.

OMG thank you for external eeprom dump and PFlash sectors 0-7 dumps!!! This is i need so much!!!

Final Drive Ratio is at 0x271FE (Sector 9) offset in your int_flash dump. Value is (4E 0C) = 0xC4E = 3150 (3.15x1000).

[Martyn]

Nice find.

Tomba, does the X17/Flex automatically correct checksums/rsa?

[S54B32]

If someone knows how to correct checksum, we can maybe repack 0PA/0DA files to flash with Winkfp. I have access to a DCT swap (with different rear ratio) to test.

[olza]

seems i hacked signature check today, thanks to this dump binarys!

[tdott]

xHP currently supports some DCT transmission and adds the possibility to change the final drive ratio.
Unfortunately I don't have an A2L file for the DCT transmission. I can read it with X17/Flex tool (MagicMotorsport). But don't know the location/value to edit.

In attachment DKG/DCT read from E9X M3.

Was this a read from a GTS flashed DCT?

Or normal Euro or NA?

[Tomba]

OMG thank you for external eeprom dump and PFlash sectors 0-7 dumps!!! This is i need so much!!!

Final Drive Ratio is at 0x271FC (Sector 8) offset in your int_flash dump. Value is (4E 0C) = 0xC4E = 3150 (3.15x1000).

No problem. Glad I could be off assistance. Thanks for pointing out the final drive ratio, helps a lot!

Nice find.

Tomba, does the X17/Flex automatically correct checksums/rsa?

Yes, it does. As far as I know currently only MAPS are able to be changed.
You can also clone gearbox control units with the software

Was this a read from a GTS flashed DCT?

Or normal Euro or NA?

I'll have to check, I believe normal European one.
You can compare 0da files from SP daten and compare "regular" file vs "GTS" file. I still think without A2L file it will be hard.