Changing the Final Drive

[UNVAXXDZ4]

Ok y'all. New to spool street here. Excited to see what the happenings are.

I have a z4 e89 6MT car. I swapped the rear end from the 3.08 to the 2.56 from a DCT car. Now my cruise doesn't work in 5th and 6th. I see some old threads about coding a DDE. Anyone want to offer up a little info on this? And if anyone out there knows how to do it we should chat!

 

[pbondar]

I had a similar problem on my E89 20i auto…changed the diff ratio and the box threw a complete wobbly..wasn’t able to solve it…

However on the 35i/35is you can use xHP to recode it..if you have a DCT..not sure how you do it on 6MT

Good luck

 

[carabuser]

It's done in the ECU tune. You can set the wheel size and gear ratios in there too. I believe that's what will be throwing the cruise control off.

If you have a custom tune then send it to me and I can try and adjust the final drive for you.

In the DCT version of the car all those calcs are carried out in the transmission, but on a 6MT car the DME handles it.

 

[carabuser]

Actually no need to send me the file, it's in the public XDF:

Set that to 2.56 and you should be good.

 

[boost135]

@UNVAXXDZ4 I want to do a manual swop soon on my 6AT is there any benefit running the 2.56 vs the 3.08/3.46.
Car will be used for the occasional drag race and street driving?

 

[pbondar]

@UNVAXXDZ4 I want to do a manual swop soon on my 6AT is there any benefit running the 2.56 vs the 3.08/3.46.
Car will be used for the occasional drag race and street driving?

I wouldn’t have thought so..best to keep those N54s spinning ….

IMHO…