2019-up 4.09 Rear Gear Swap

[Dave2013M3]

I’m thinking of getting a huffer myself. Would 3.73 work or staying with 3.55 work better in your opinion.

I think the 3.55's would be better.

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[AZlb5.0]

Go Whipple/Edelbrock/VMP if 3.55. Centri is not great with the 18+ MT82 gearing (hence why I switched).

I was thinking of ESS with 9lb spring

I think the 3.55's would be better.

Cool

 

[paulmustangv6]

Definitely interested in this, you’re the first one I’ve seen to successfully navigate programming a ratio greater than 4.09 in a 19+ car.

4.56 Yukon ring and pinion
2020 EU spec Mustang GT
This procedure works flawlessly for me - Rev Match works - no DTC's.

I take no responsibility if it does not work as expected, so only at your own risk.
Before you start the process, make sure the battery is fully charged, for safety put a battery charger.

The process requires Hptuners and Forscan

FORSCAN
*clear all DTC's in Forscan

It was not necessary for me to change Bdy CM AS BUILT format (it switched by itself) when the axle offset was set to 4.560 in the BdyCM module

Go to BdyCM module configuration

Then set axle value to 4.56 (then run service procedure)

*clear DTC's in Forscan

HPTUNERS
Use final Ratio - Calibration (and change the additional three values)
*Min/Max Ratio I wrote this just as a test, but it works for me without any errors.
save as, then write vehicle

Back to FORSCAN
*clear all DTC's in Forscan

Go to ForscanService functions:
TCU Module Reset (run service procedure)
PCM Clear Transmission Adaptive Tables (run service procedure)
PCM Reset All Adaptations

(didn't have to reset PCM Module, if there is an error, it must be reset as well)

*clear DTC's in Forscan
then go to BdyCm AS BUILT format

Check AS BUILT (726-15-01)

Yukon 4.56 ring and pinion - followthe break in instructions as all new gear sets require a break-in period to prevent damage from overheating.

 

[NeverSatisfied]

Nice job!

When you write with HPTuners, can a dealer see it's been "flashed"?

 

[Dave2013M3]

Unfortunately 2020 on up can't change gear ratio in Forscan.

 

[paulmustangv6]

Unfortunately 2020 on up can't change gear ratio in Forscan.

As mentioned works well on my 2020 EU spec GT

 

[Dave2013M3]

As mentioned works well on my 2020 EU spec GT

Interesting...the guy that installed my 4.09s said that the Forscan changes won't work with the 2020 on up. No issues as I had the ProCal tool with my Ford Performance tune.

 

[paulmustangv6]

Interesting...the guy that installed my 4.09s said that the Forscan changes won't work with the 2020 on up. No issues as I had the ProCal tool with my Ford Performance tune.

Please read back the whole process description accurately.
Successful change require 2 different device and software.

PCM trough Hptuners

BCM trough Forscan

hope this helps

 

[Dave2013M3]

Please read back the whole process description accurately.

Successful change require 2 different device and software.

PCM trough Hptuners
then
BCM trough Forscan

hope this helps

I already did it with the Pro Cal.

 

[NeverSatisfied]

I already did it with the Pro Cal.

what you’re missing is pro cal only allows up to 4.09.

he is the first person I’ve seen to figure out how to get past the 4.09 barrier on a rev match car. It takes forscan and hptuners. Pro cal isn’t involved in this solution .

 

[Dave2013M3]

what you’re missing is pro cal only allows up to 4.09.

he is the first person I’ve seen to figure out how to get past the 4.09 barrier on a rev match car. It takes forscan and hptuners. Pro cal isn’t involved in this solution .

No I realize this...to be frank 4.09s on a street car is more than enough. I am having traction issues when temps drop in the 60deg range with Mich PSS 305/35/19's.

 

[Cobra Jet]

4.56 Yukon ring and pinion
2020 EU spec Mustang GT
This procedure works flawlessly for me - Rev Match works - no DTC's.

I take no responsibility if it does not work as expected, so only at your own risk.
Before you start the process, make sure the battery is fully charged, for safety put a battery charger.

The process requires Hptuners and Forscan

FORSCAN
*clear all DTC's in Forscan

It was not necessary for me to change Bdy CM AS BUILT format (it switched by itself) when the axle offset was set to 4.560 in the BdyCM module

Go to BdyCM module configuration

Then set axle value to 4.56 (then run service procedure)

*clear DTC's in Forscan

HPTUNERS
Use final Ratio - Calibration (and change the additional three values)
*Min/Max Ratio I wrote this just as a test, but it works for me without any errors.
save as, then write vehicle

Back to FORSCAN
*clear all DTC's in Forscan

Go to ForscanService functions:
TCU Module Reset (run service procedure)
PCM Clear Transmission Adaptive Tables (run service procedure)
PCM Reset All Adaptations

(didn't have to reset PCM Module, if there is an error, it must be reset as well)

*clear DTC's in Forscan
then go to BdyCm AS BUILT format

Check AS BUILT (726-15-01)

Yukon 4.56 ring and pinion - followthe break in instructions as all new gear sets require a break-in period to prevent damage from overheating.

That there is some excellent 4.56 rear diff Tech and advice for sure! Thanks for sharing with us!!!

 

[Dave2013M3]

What would be interesting is if this Forscan sequence will work with the 2024 Mustangs?

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