Thoughts on 4.09 gear

[Niz55]

I have been really thinking of replacing the 3.73 with 4.09. this car can definitely use some more low end pull. Only issue I have is the speedometer will be off by 5 mph. Does ford offer calibration for the new gears?

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[cosmo]

https://www.mustang6g.com/forums/th...gear-to-4-56-in-my-gt350.104766/#post-2265091

I'd ask this guy.

 

[Mach4.6]

Not worth it IMO, would maybe consider 3.90 gears?

 

[Hack]

I think 3.90 or 4.09 would be too subtle of a change and you would barely notice a difference. 4.56 or 4.88 would be better.

 

[Niz55]

Don't see a 3.90 gear from frpp.

 

[Niz55]

After reading through his thread I think I will be sticking with the OEM 3.73. lol

 

[Mach4.6]

Don't see a 3.90 gear from frpp.

They're made by US Gear
https://www.usgear.com/products/ring-and-pinion/ford-super-8-8-irs-3-91-lightning-series

 

[guzie]

I have been really thinking of replacing the 3.73 with 4.09. this car can definitely use some more low end pull. Only issue I have is the speedometer will be off by 5 mph. Does ford offer calibration for the new gears?

You can adjust speedo calibration using Forscan. There is a long thread on using the tool. The speedo calibration is handled by the body module and not the ECU so hand held tuners can’t tweak for gear changes anymore. I recalibrated mine after switching to GT350R spec tire sizes. My speedo was off by 3. Not anymore.

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