4.09 Axle Ratio Computer Programming in 2021 or newer?

[involutions]

I've done a little searching, but can't find a definitive answer about changing the axle ratio in a 2021 or newer car without an aftermarket tune. In my 2015 I was able to use forscan, but no longer have the program or OBD connector.

My question is... Is there a way to program the BCM and/or PCM to accept a 4.09 axle without installing an aftermarket tune? Can the dealer make this change? Will Forscan do this? Has anyone on this forum done this? By the way, my car is a 2022.

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[ice445]

Nope, they changed it to where it has to be updated in the pcm for the active rev matching feature (even if you don't use it). It probably is plugged into torque calculations as well for the advancetrac.
I think the cheapest way to do this now is using pcmtec, this should allow you to change the relevant value while retaining the normal stock tune characteristics.

 

[WD Pro]

I believe there is a option to do this, start reading this thread starting with this post :

https://www.mustang6g.com/forums/threads/4-09-gears-in-2019-m6-questions.170200/page-3#post-3500552

And don’t get bored, make sure you get to post #70 onwards for the confirmation

WD

 

[ice445]

I believe there is a option to do this, start reading this thread starting with this post :

https://www.mustang6g.com/forums/threads/4-09-gears-in-2019-m6-questions.170200/page-3#post-3500552

And don’t get bored, make sure you get to post #70 onwards for the confirmation

WD

Good info (and I've tested it too) but the procal is still technically flashing the pcm and bcm during that process

 

[WD Pro]

Good info (and I've tested it too) but the procal is still technically flashing the pcm and bcm during that process

Thanks for the further confirmation - I really like this option rather than having to go ‘aftermarket’ (especially in the U.K.)

Cheers,

WD

 

[WildHorse]

FORscan , FORscan , FORscan. then reset the BCM.

 

[WD Pro]

FORscan , FORscan , FORscan. then reset the BCM.

I’m not totally convinced that I have read about someone who has actually done / tested / confirmed that process works on a later car ?

But I would defo welcome the confirmation that it’s an option for me

WD

 

[Rolls]

I believe you can override the axle / differential value in the tune itself via the following scalars in PCMTEC.

Set CDP requires to 0 and set the rear axle ratio manually.

This likely would only only work for a manual vehicle.

There is also a lookup table for precise ratios which are used in various parts of the code. I don't know what would happen if you changed say a 3.555 to 4.875 but that might "hack" the tune to change the ratio also.

All of these scalars are present in the 22+ calibrations in PCMTEC that I checked.

I suspect there are several other scalars present as well, a good way to find them would be to compare a PP1 and PP2 (or some cal that has a different diff ratio in the stock calibration to see what Ford has changed). You will likely find everything you need that way.

Another good hack is calibration tools > view all scalars. Ctrl + a, ctrl + c, wait a minute. Go to excel. Ctrl + V

Then search for the diff ratio and you'll find all the auFs that have that number in them.

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